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Upcoming Events

Event Date and Location Summary
Benjamin Monreal (CWRU) Tue. March 19th, 2019
11:30 am-12:30 pm
at Foldy Room

Giant telescopes, exoplanets, and astronomy in the 2020s

Maura McLaughlin (West Virginia University) Tue. April 2nd, 2019
11:30 am-12:30 pm
at Foldy Room

The NANOGrav 11-year Data Set: New Insights into Galaxy Growth and Evolution

James Wells (University of Michigan-Ann Arbor) Tue. April 9th, 2019
11:30 am-12:30 pm
at Foldy Room
Yue Zhang (Fermilab) Tue. April 16th, 2019
11:30 am-12:30 pm
at Foldy Room
Jacob Seiler (Swinburne University of Technology, Melbourne) Tue. May 7th, 2019
11:30 am-12:30 pm
Bharat Ratra (Kansas State University) Fri. September 6th, 2019
11:30 am-12:30 pm
at Foldy room

Cosmological Seed Magnetic Field from Inflation

A cosmological magnetic field of nG strength on Mpc length scales could be the seed magnetic field needed to explain observed few microG large-scale galactic magnetic fields. I first briefly review the observational and theoretical motivations for such a seed field, two galactic magnetic field amplification models, and some non-inflationary seed field generation scenarios. I then discuss an inflation magnetic field generation model. I conclude by mentioning possible extensions of this model as well as potentially observable consequences.

Past Events

Event Date Summary
Benjamin Monreal (CWRU) Tue. March 19th, 2019
11:30 am-12:30 pm

Giant telescopes, exoplanets, and astronomy in the 2020s

Bhupal Dev (Washington University) Tue. March 5th, 2019
11:30 am-12:30 pm

New Physics at Neutrino Telescopes

Abstract: The recent observation of high-energy neutrinos at the IceCube neutrino telescope has opened a new era in neutrino astrophysics.  Understanding all aspects of these events is very important for both Astrophysics and Particle Physics ramifications.  In this talk, I will discuss a few possible new physics scenarios, such as dark matter, leptoquarks and supersymmetry, that could be probed using the IceCube data.  I will also relate this to the puzzling observation of two upgoing EeV events recently made by the ANITA experiment,

Brian Batell (University of Pittsburgh ) Tue. February 26th, 2019
11:30 am-12:30 pm
Breaking Mirror Hypercharge in Twin Higgs Models
 
The Twin Higgs is a novel framework to understand the stability of the Higgs mass in the face of increasingly stringent LHC bounds on colored top partners. Two principal structural questions in this framework concern the nature of the twin hypercharge gauge symmetry and the origin of the Z2 symmetry breaking needed to achieve the correct vacuum alignment. After an introduction to this framework, a simple extension of the Mirror Twin Higgs model with an exact Z2 symmetry is presented in which a new scalar field in the twin sector spontaneously breaks both twin hypercharge and Z2.  
Aaron Pierce (University of Michigan-Ann Arbor) Tue. February 19th, 2019
11:30 am-12:30 pm
Supersymmetry, Hidden Sectors, and Baryogenesis
 
Abstract:  Supersymmetry has been a primary target for the experiments at the Large Hadron Collider.  We review what the absence of supersymmetric signals thus far implies for supersymmetric extensions to the Standard Model.  We discuss ways in which supersymmetry might still have important consequences for our Universe — even if it does not completely explain the hierarchy between strength of gravity and the other forces.  As an example, we discuss how a supersymmetric extension might be responsible for generating the observed symmetry between matter and anti-mattter.
Riccardo Penco (Carnegie Mellon University) Tue. February 12th, 2019
11:30 am-12:30 pm

Constraining the gravitational sector with black hole perturbations

Joshua Berger (University of Pittsburgh) Tue. February 5th, 2019
11:30 am-12:30 am
Searching for the dark sector in neutrino detectors
 
Abstract: Dark matter has thus far eluded attempts to determine its non-gravitational interactions, putting strong constraints on a minimal dark sector. I present models of non-minimal dark sectors that could elude current searches, but be seen in current or near future neutrino experiments. I begin by presenting a comprehensive, ongoing phenomenological study of models in which dark matter can annihilate into other forms of dark matter, leading to a flux of energetic (boosted) dark matter (BDM). Such dark matter could deposit enough energy to be detected in large neutrino detectors such as Super-Kamiokande and DUNE.
James Bonifacio (CWRU) Tue. January 22nd, 2019
11:30 am-12:30 pm

Shift Symmetries in (Anti) de Sitter Space

Alexis D. Plascencia (CWRU) Tue. January 15th, 2019
11:30 am-12:30 pm

Tau-philic dark matter coannihilation at the LHC and CLIC 

 

Abstract: We will discuss a set of simplified models of dark matter with three-point interactions between dark matter, its coannihilation partner and the Standard Model particle, which we take to be the tau lepton. The contribution from dark matter coannihilation is highly relevant for a determination of the correct relic abundance. Although these models are hard to detect using direct and indirect detection, we will show that particle colliders can probe large regions in the parameter space. Some of the models discussed are manifestly gauge invariant and renormalizable,

Stephane Coutu (Penn State) Tue. December 4th, 2018
11:30 am-12:30 pm

Abstract: 

Host: Covault

Mark B. Wise (Caltech) Tue. November 27th, 2018
11:30 am-12:30 pm
Loop induced inflationary non-Gaussianites that give rise to an  enhanced galaxy power spectrum at small wave-vectors
 
Abstract:  I outline the calculation of non-Gaussian mass density fluctuations that arise from one-loop Feynman diagrams in a de Sitter background.  Their impact on the distribution of galaxies on very large length scales (i.e. l > 200/ h Mpc) is discussed. The role that  symmetries of the de Sitter metric play in determining the form of the power spectrum,  bi-spectrum and tri-spectrum of primordial curvature perturbations is emphasized.

Host: Fileviez Perez

Jure Zupan (University of Cincinnati) Tue. November 20th, 2018
11:30 am-12:30 pm

 Effective field theories for dark matter direct detection

Abstract:

I will discuss the nonperturbative matching of the effective field theory describing dark matter interactions with quarks and gluons to the effective theory of nonrelativistic dark matter interacting with nonrelativistic nucleons. In general, a single partonic operator already matches onto several nonrelativistic operators at leading order in chiral counting. Thus, keeping only one operator at the time in the nonrelativistic effective theory does not properly describe the scattering in direct detection. Moreover, the matching of the axial–axial partonic level operator, as well as the matching of the operators coupling DM to the QCD anomaly term,

Jonathan Ouellet (MIT) Tue. November 13th, 2018
11:30 am-12:30 pm

First Results from the ABRACADABRA-10cm Prototype

The evidence for the existence of Dark Matter is well supported by
many cosmological observations. Separately, long standing problems
within the Standard Model point to new weakly interacting particles to
help explain away unnatural fine-tunings. The axion was originally
proposed to explain the Strong-CP problem, but was subsequently shown
to be a strong candidate for explaining the Dark Matter abundance of
the Universe. ABRACADABRA is a proposed experiment to search for
ultralight axion Dark Matter, with a focus on the mass range
10^{-14} ~<

Francesc Ferrer (Washington University) Tue. October 30th, 2018
11:30 am-12:30 pm

Primordial black holes in the wake of LIGO

The detection of gravitational waves from the merger of black holes of ~30 solar masses has reignited the interest of primordial black holes (PBHs) as the source of the dark matter in the universe. We will review the existing constraints on the abundance of PBHs and the implications for several fundamental physics scenarios. A small relic abundance of heavy PBHs may play and important role in the generation of cosmological structures, and we will discuss how such a PBH population can be generated by the collapse of axionic topological defects.

Xiaoju Xu (University of Utah) Tue. October 16th, 2018
11:30 am-12:30 pm

Multivariate Dependent Halo and Galaxy Assembly Bias

Galaxies form in dark matter halos, and their properties and
distributions are connected to the host halos. With a prescription of
the galaxy-halo relation and the theoretically known halo clustering
(e.g., from N-body simulations), galaxy clustering data from large
galaxy surveys can be modeled to learn about galaxy formation and
cosmology. In the above halo-based model, it is usually assumed that
the statistical distribution of galaxies inside halos only depends on
halo mass. However, it is found that in addition to mass halo
clustering also depends on the formation history and environment of
halos,

Brad Benson (University of Chicago) Tue. October 9th, 2018
11:30 am-12:30 pm

New Results from the South Pole Telescope

I will give an overview of the South Pole Telescope (SPT), a 10-meter diameter telescope at the South Pole designed to measure the cosmic microwave background (CMB).  The SPT recently completed 10 years of observations, over which time it has been equipped with three different cameras: SPT-SZ, SPTpol, and SPT-3G. I will discuss recent results from the SPT-SZ and SPTpol surveys, including: an update on the SPT Sunyaev-Zel’dovich (SZ) cluster survey, and joint analyses with the optical dark energy survey (DES); a comparison of CMB measurements between SPT-SZ and the Planck satellite;

Tim Linden (Ohio State University) Tue. October 2nd, 2018
11:30 am-12:30 pm

2018 Michelson Postdoctoral Prize Lecture 2

The Rise of the Leptons: Emission from Pulsars will Dominate the next Decade of TeV Gamma-Ray Astronomy

HAWC observations have detected extended TeV emission coincident with the Geminga and Monogem pulsars. In this talk, I will show that these detections have significant implications for our understanding of pulsar emission. First, the spectrum and intensity of these “TeV Halos” indicates that a large fraction of the pulsar spindown energy is efficiently converted into electron-positron pairs. This provides observational evidence necessitating pulsar interpretations of the rising positron fraction observed by PAMELA and AMS-02.

Mahmoud Parvizi (Vanderbilt University) Tue. September 25th, 2018
11:30 am-12:30 pm

Cosmological Observables via Non-equilibrium Quantum Dynamics in Non-stationary Spacetimes

Abstract: 

In nearly all cases cosmological observables associated with quantum matter fields are computed in a general approximation, via the standard irreducible representations found in the operator formalism of particle physics, where intricacies related to a renormalized stress-energy tensor in a non-stationary spacetime are ignored. Models of the early universe also include a hot, dense environment of quantum fields where far-from-equilibrium interactions manifest expressions for observables with leading terms at higher orders in the coupling. A more rigorous treatment of these cosmological observables may be carried out within the alternative framework of algebraic quantum field theory in curved spacetime,

Miguel Zumalacarregui (UC Berkeley & IPhT Saclay) Tue. September 18th, 2018
11:30 am-12:30 pm

The Dark Universe in the Gravitational Wave Era
Evidence shows that we live in a universe where 95% of the matter and energy is of unknown nature. Right from the onset, Gravitational Wave (GW) astronomy is shaping our understanding of the dark universe in several ways: GW signals of black hole mergers have resurrected the idea of Dark Matter being made of primordial black holes, while multi-messenger GW astronomy has generated novel ways to test Dark Energy and the fundamental properties of gravity. I will discuss the impact of gravitational waves on the landscape of gravitational theories,

Andre De Gouvea (Northwestern Univ.) Fri. September 7th, 2018
12:45 pm-1:45 pm

Chiral Dark Sectors, Neutrino Masses, and Dark Matter

I discuss the hypothesis that there are new chiral fermions particles that transform under a new gauge group. Along the way, I present one mechanism for constructing nontrivial, chiral gauge theory and explore the phenomenology – mostly related to nonzero neutrino masses and the existence of dark matter – associated to a couple of concrete example.

Host: Fileviez Perez

Anastasia Fialkov (Harvard Univ.) Tue. August 7th, 2018
11:30 am-12:30 pm

SHINING LIGHT INTO COSMIC DARK AGES

The first billion years is the least-explored epoch in cosmic history. The first claimed detection of the 21 cm line of neutral hydrogen by EDGES (announced at the end of February this year) – if confirmed – would be the first time ever that we witness star formation at cosmic dawn. Join Dr. Fialkov as she discusses theoretical modeling of the 21 cm signal, summarizes the status of the field after the EDGES detection, and shares thoughts on prospects for future detections of this line.

Amy Connolly (The Ohio State University) Tue. May 8th, 2018
11:30 am-12:30 pm
High Energy Neutrino Astronomy through Radio Detection 

Multimessenger astronomy has entered an exciting new era with the recent discovery of both gravitational waves and cosmic neutrinos.  I will focus on neutrinos as particles that can uniquely probe cosmic distances at the highest energies.  While optical Cerenkov radiation has been used for decades in neutrino experiments, the radio Cerenkov technique has emerged in the last 15 years as the most promising for a long-term program to push the neutrino frontier by over a factor of 1000 in energy.   I will give an overview of the current status and future of the radio neutrino program,

Stuart Raby (Ohio State University) Tue. May 1st, 2018
11:30 am-12:30 am

Fitting amu and B physics anomalies with a Z’ and a Vector-like 4th family in the Standard Model

The Standard Model is very successful.  Nevertheless, there are some, perhaps significant, discrepancies with data.

A particularly interesting set of discrepancies hints at new physics related to muons. I will review the data and recent

NP models trying to fit the data.  Then I will discuss a very simple model which is motivated by heterotic string constructions.

Tyce DeYoung (Michigan State University) Tue. April 24th, 2018
11:30 am-12:30 am

First light at the IceCube Neutrino Observatory
The IceCube Neutrino Observatory, the world’s largest neutrino detector, monitors a cubic kilometer of glacial ice below the South Pole Station to search for very high energy neutrinos from the astrophysical accelerators of cosmic rays.  Since its commissioning in 2011, IceCube has discovered a flux of TeV-PeV scale astrophysical neutrinos, at a level with significant implications for our understanding of the dynamics of the non-thermal universe.  The sources of this flux have remained elusive, however.  In the last six months, hints to the identity of at least some of the sources may have begun to emerge,

Camille Avestruz (Kavli Institute for Cosmological Physics, University of Chicago) Tue. April 17th, 2018
11:30 am-1:30 pm
Computationally Probing Large Structures
We can constrain cosmological parameters by measuring patterns in the large scale structure of our universe, which are governed by the competition between gravitational collapse and the accelerated expansion of our universe.  The most massive collapsed structures are clusters of galaxies, comprised of hundreds to thousands of galaxies.  For galaxy clusters, the telltale cosmological pattern is simply their number count as a function of mass and time.  In this talk, I will discuss the challenges in using galaxy clusters as a probe for cosmology.  We address these challenges through computational methods that explore galaxy formation processes such as energy feedback from active galactic nuclei,
Hayden Lee (Harvard University) Tue. April 3rd, 2018
11:30 am-12:30 am
Collider Physics for Inflation
Cosmological correlation functions encode the spectrum of particles during inflation, in analogy to scattering amplitudes in colliders. Particles with masses comparable to the Hubble scale lead to distinctive signatures on non-Gaussianities that reflect their masses and spins. In addition, there exists a special class of partially massless particles that have no flat space analog, but could have existed during inflation. I will describe their key spectroscopic features in the soft limits of correlation functions, and discuss scenarios in which they lead to observable non-Gaussianity.
Segev BenZvi (University of Rochester) Tue. March 27th, 2018
11:30 am-12:30 am

The Latest Results from the HAWC Very High-Energy Gamma-ray Survey
The High Altitude Water Cherenkov (HAWC) observatory, located in central
Mexico, is conducting a wide-angle survey of TeV gamma rays and cosmic
rays from two-thirds of the sky. TeV gamma rays are the highest energy
photons ever observed and provide a unique window into the non-thermal
universe. These very high energy photons allow HAWC to conduct a broad
science program, ranging from studies of particle acceleration in the
Milky Way to searches for new physics beyond the Standard Model. In this
talk,

Cliff Cheung (Caltech) Tue. March 20th, 2018
11:30 am-12:30 pm
Unification from Scattering Amplitudes
 
The modern S-matrix program offers an elegant approach to bootstrapping quantum field theories without the aid of an action.  While most progress has centered on gravity and gauge theory, similar ideas apply to effective field theories (EFTs).  Sans reference to symmetry or symmetry breaking, we show how certain EFTs can be derived directly from the properties of the tree-level S-matrix, carving out a theory space of consistent EFTs from first principles.  Furthermore, we argue that the S-matrix encodes a hidden unification of gravity, gauge theory, and EFTs.  In particular, starting from the tree-level S-matrix of the mother of all theories,
John Beacom (The Ohio State University) Tue. March 6th, 2018
11:30 am-12:30 pm

A New Era for Solar Neutrinos
Abstract: Studies of solar neutrinos have been tremendously important, revealing the nature of the Sun’s power source and that its neutrino flux is strongly affected by flavor mixing.  Nowadays, one gets the impression that this field is over.  However, this is not due to a lack of interesting questions; it is due to a lack of experimental progress.  I show how this can be solved, opening opportunities for discoveries in particle physics and astrophysics, simultaneously.

Lindley Winslow (MIT) Wed. February 28th, 2018
1:30 pm-2:00 pm

First Results from CUORE: Majorana Neutrinos and the Search for Neutrinoless Double-Beta Decay
The neutrino is unique among the Standard Model particles. It is the only
fundamental fermion that could be its own antiparticle, a Majorana particle. A
Majorana neutrino would acquire mass in a fundamentally different way than the
other particles and this would have profound consequences to particle physics and
cosmology. The only feasible experiments to determine the Majorana nature of the
neutrino are searches for the rare nuclear process neutrinoless double-beta decay.
CUORE uses tellurium dioxide crystals cooled to 10 mK to search for this rare
process.

Richard Ruiz (IPPP-Durham, UK) Tue. February 20th, 2018
11:30 am-12:30 am

LeftRight Symmetry: At the Edges of Phase Space and Beyond

The LeftRight Symmetric model (LRSM) remains one of the best motivated completions of the Standard Model of Particle Physics. Thus far, however, data from the CERN Large Hadron Collider (LHC) tell us that new particles, if they are still accessible, must be very heavy and/or very weakly coupled. Interestingly, these regions of parameter space correspond to collider signatures that are qualitatively and quantitatively different from those developed in pre-LHC times.

Andrew J. Long (Kavli Institute for Cosmological Physics, University of Chicago) Tue. February 13th, 2018
11:30 am-12:30 am
Testing baryons from bubbles with colliders and cosmology  
“Why is there more matter than antimatter?”  This simple question is arguably the most longstanding and challenging problem in modern cosmology, but with input from the next generation of particle physics experiments we may finally have an answer!  In the talk I will discuss how precision measurements of the Higgs boson at the LHC and future high energy collider experiments will be used to test the idea that the matter-antimatter asymmetry arose during the electroweak phase transition in the fractions of a second after the big bang.  Other cosmological phase transitions can also provide the right environment for generating the matter excess. 
Ayres Freitas (University of Pittsburgh) Tue. February 6th, 2018
11:30 am-12:30 am

Radiative Corrections in Universal Extra Dimensions

Universal extra dimensions is an interesting extension of the Standard Model
that is naturally protected from electroweak precision constraints and provides
a natural dark matter candidate. Its phenomenology at the LHC is strongly
affected by radiative corrections. On one hand, QCD corrections are important
for understanding the production of heavy gluons and quarks, which are the
particles with the largest production rates at the LHC. On the other hand,
radiative corrections crucially modify the mass spectrum and interactions of the
heavy resonances. This talk will describe recent progress on both of these
fronts.

David McKeen (University of Pittsburgh) Tue. January 30th, 2018
11:30 am-12:30 am

Neutrino Portal Dark Matter

Dark matter that interacts with the standard model (SM) through the “neutrino portal” is a possibility that is relatively less well studied than other scenarios. In such a setup, the dark matter communicates with the SM primarily through its interactions with neutrinos. In this talk, I will motivate neutrino portal dark matter and discuss some new tests of this possibility.

Anders Johan Andreassen (Harvard University) Tue. January 23rd, 2018
11:30 am-12:30 pm

Tunneling in Quantum Field Theory and the Ultimate Fate of our Universe

One of the most concrete implications of the discovery of the Higgs boson is that, in the absence of physics beyond the standard model, the long-term fate of our universe can now be established through precision calculations. Are we in a metastable minimum of the Higgs potential or the true minimum? If we are in a metastable vacuum, what is its lifetime? To answer these questions, we need to understand tunneling in quantum field theory.This talk will give an overview of the interesting history of tunneling rate calculations and all of its complications in calculating functional determinants of fluctuations around the bounce solutions.

Dragan Huterer (U. Michigan) Fri. December 1st, 2017
12:45 pm-1:45 pm

title and abstract tba

Arthur Kosowsky (Pittsburgh) Tue. November 28th, 2017
11:30 am-12:30 pm

title and abstract tba

Simone Aiola (Princeton) Tue. November 14th, 2017
11:30 am-12:30 pm

Cosmology with ACTPol and AdvACT

The bolometric polarimeter at the focal plane of the Atacama Cosmology Telescope allows us to map the Cosmic Microwave Background (CMB) with high signal-to-noise both in temperature and polarization.  In this talk, I will present the data-reduction pipeline, highlighting the importance of making maximum-likelihood unbiased CMB maps. I will show the two-season ACTPol cosmological results presented in Louis et al. (2017), Sherwin et al. (2017), and Hilton et al. (2017) and describe the current effort to finalize the analysis of the ACTPol dataset. I will conclude with preliminary results from the ongoing AdvACT survey,
James Bonifacio (Oxford and CWRU) Tue. October 31st, 2017
11:30 am-12:30 pm

Title: Amplitudes for massive spinning particles
 Abstract: I will review a method for constructing scattering amplitudes for spinning particles and then discuss how these amplitudes can be used to constrain massive gravity and theories containing higher-spin particles.

Lloyd Knox (UC Davis) Tue. October 17th, 2017
11:30 am-12:30 pm

The Standard Cosmological Model: A Status Report

Overall, the standard cosmological model has enjoyed enormous empirical success. But there are  a number of indicators that we might be missing something. These include the large-scale cosmic microwave background (CMB) “anomalies”, and two to three sigma discrepancies between cosmological parameters derived from larger angular scales of the CMB vs. smaller angular scales, CMB lensing potential reconstruction vs. CMB power spectra, data from the Planck satellite vs. data from the South Pole Telescope, and CMB-calibrated predictions for  the current rate of expansion vs. more direct measurements. I will introduce the standard cosmological model,

Rachel Bezanson (Pittsburgh) Tue. October 10th, 2017
11:30 am-12:30 pm
Title: The Surprisingly Complex Lives of Massive Galaxies
 
Abstract: Massive galaxies reside in the densest and most evolved regions of the Universe, yet we are only beginning to understand their formation history. Once thought to be relics of a much earlier epoch, the most massive local galaxies are red and dead ellipticals, with little ongoing star formation or organized rotation. In the last decade, observations of their assumed progenitors have demonstrated that the evolutionary histories of massive galaxies have been far from static. Instead, billions of years ago, massive galaxies were morphologically different: compact, possibly with more disk-like structures,
Tiziana Di Matteo (Carnegie Mellon) Tue. September 26th, 2017
11:30 am-12:30 pm
The next massive galaxy and quasar frontier at the Cosmic Dawn

Many of the advances in our understanding of cosmic structure have come
from direct computer modeling. In cosmology, we need to develop computer
simulations that cover this vast dynamic range of spatial and time
scales. I will discuss recent progress in cosmological hydrodynamic
simulations of galaxy formation at unprecedented volumes and
resolution. I will focus on predictions for the first quasars and
their host galaxies in the BlueTides simulation. 

Laura Gladstone (CWRU) Tue. September 19th, 2017
11:30 am-12:30 pm
Neutrinos: cool, cold, coldest
 
In all of particle physics, neutrinos are some of the most ghostly particles we’ve detected. While the story of their discovery was pretty cool in itself, some modern experiments are even cooler. 
 
The IceCube experiment, located at the geographic South Pole, was originally designed to collect astro-particle data, especially by looking for neutrino point sources as potential sources of the highest energy cosmic rays. But because of its immense fiducial volume, IceCube can collect high-statistic neutrino data, and thus measure oscillation parameters with precision that rivals dedicated oscillation experiments. 
Liang Wu, University California Berkeley, MPPL2,Giant nonlinear optical responses in Weyl semimetals Tue. September 12th, 2017
11:30 pm-12:30 pm

Giant nonlinear optical responses in Weyl semimetals

Recently Weyl quasi-particles have been observed in transition metal monopnictides (TMMPs) such as TaAs, a class of noncentrosymmetric materials that heretofore received only limited attention. The question that arises now is whether these materials will exhibit novel, enhanced, or technologically applicable properties. The TMMPs are polar metals, a rare subset of inversion- breaking crystals that would allow spontaneous polarization, were it not screened by conduction electrons. Despite the absence of spontaneous polarization, polar metals can exhibit other signatures, most notably second-order nonlinear optical polarizability, leading to phenomena such as second-harmonic generation (SHG).

Gabriela Marques, National Observatory of Rio de Janeiro and CWRU Tue. September 5th, 2017
11:30 am-12:30 pm

title and abstract tba

Sarah Shandera (Penn State) Tue. May 9th, 2017
11:00 am-12:00 pm

Cosmological open quantum systems

Our current understanding of the universe relies on an inherently quantum origin for the rich, inhomogeneous structure we see today. Inflation (or any of the alternative proposals for the primordial era) easily generates a universe exponentially larger than what we can observe. In other words, the modes that are observationally accessible make up an open quantum system. I will discuss what we might learn by thinking about the universe in this way, even though the quantum structure is probably not observable.

Ema Dimastrogiovanni (CWRU) Tue. April 25th, 2017
11:00 am-12:00 pm

Primordial gravitational waves: Imprints and search

Discussed will be some interesting scenarios for the generation of gravitational waves from inflation and the characteristic imprints we can search with upcoming cosmological observations.

Matthew Johnson (Perimeter Institute) Tue. April 18th, 2017
11:00 am-12:00 pm

Mapping Ultra Large Scale Structure

Anomalies in the CMB on large angular scales could find an explanation in terms of pre-inflationary physics or intrinsic statistical anisotropies. However, due to cosmic variance it is difficult to conclusively test many of these ideas using the primary cosmic microwave background (CMB) alone. In this talk, I will outline a program to place stringent observational constraints on theories that predict ultra-large scale structure or statistical anisotropies using the secondary CMB (the Sunyaev Zel’dovich effect, polarization form the post-reionization era, lensing, etc.) and tracers of large-scale structure. These methods will become accessible with next-generation CMB experiments and planned galaxy surveys.

David Chuss (Villanova) Tue. April 11th, 2017
11:00 am-12:00 pm

The Cosmology Large Angular Scale Surveyor (CLASS)

Precise observations of the cosmic microwave background have played a leading role in the development of the LCDM model of cosmology, which has been successful in describing the universe’s energy content and evolution using a mere six parameters. With this progress have come hints that the universe underwent an inflationary epoch during its infancy.  Cosmic inflation is predicted to produce a background of gravitational waves that would imprint a distinct polarized pattern on the cosmic microwave background (CMB). Measurement of this polarized signal would provide the first direct evidence for inflation and would provide a means to study physics at energy scales around the predicted GUT scale. 

Donghui Jeong (Penn State) Tue. April 4th, 2017
11:00 am-12:00 pm

Non-linearities in large-scale structure: Induced gravitational waves, non-linear galaxy bias

I will present my recent work on non-linearities in large-scale structures of the Universe. For the first part, I will discuss the gauge dependence of the scalar-induced tensor perturbations and its implication on searching the primordial gravitational wave signature from the large-scale structure. For the second part of the talk, I will give a brief overview of the recent review on large-scale galaxy bias (Desjacques, Jeong & Schmidt, 1611.09787) that contains a complete expression for the perturbative bias expansion that must hold on large scales.

Ben Monreal (CWRU) Tue. March 28th, 2017
11:00 am-12:00 pm

Nuclei, neutrinos, and microwaves: searching for the neutrino mass in tritium decay

When Enrico Fermi published his theory of beta decay in 1934—what we now call the weak interaction—he suggested how experiments could measure the neutrino mass: by looking at the shape of the energy distribution of beta decay electrons.  We’re still doing exactly that!  I will talk about the state of the art of tritium beta decay electron measurements: the KATRIN experiment, which starts science runs soon with a molecular tritium source towards sub-0.3 eV sensitivity; and the Project 8 experiment, which aims to develop a future atomic tritium experiment sensitive to neutrino masses below 0.05 eV.  

Mauricio Bustamante (CCAPP, OSU) Tue. March 21st, 2017
11:00 am-12:00 pm

Prospecting for new physics with high-energy astrophysical neutrinos

High-energy astrophysical neutrinos, recently discovered by IceCube, are fertile ground to look for new physics.  Due to the high neutrino energies — tens of TeV to a few PeV — we can look for new physics at unexplored energies.  Due to their cosmological-scale baselines — Mpc to Gpc — tiny new-physics effects, otherwise unobservable, could accumulate and become detectable.  Possibilities include neutrino decay, violation of fundamental symmetries, and novel neutrino-neutrino interactions.  I will show that the spectral features, angular distribution, and flavor composition of neutrinos could reveal the presence of new physics and,
Robert Caldwell (Dartmouth) Tue. March 7th, 2017
11:00 am-12:00 pm

Cosmology with Flavor-Space Locked Fields

We present new models of cosmic acceleration built from a cosmological SU(2) field in a flavor-space locked configuration. We show that such fields are gravitationally birefringent, and absorb and re-emit gravitational waves through the phenomenon of gravitational wave — gauge field oscillations. As a result, a cosmological SU(2) field leaves a unique imprint on both long-wavelength gravitational waves of primordial origin as well as high frequency waves produced by astrophysical sources. We show that these effects may be detected in the future using the cosmic microwave background and gravitational wave observatories.

Matthew Baumgart (Perimeter Institute) Tue. February 14th, 2017
11:00 am-12:00 pm

De Sitter Wavefunctionals and the Resummation of Time

The holographic RG of Anti-De Sitter gives a powerful clue about the underlying AdS/CFT correspondence. The question is whether similar hints can be found for the heretofore elusive holographic dual of De Sitter. The framework of stochastic inflation uses nonperturbative insight to tame bad behavior in the perturbation series of a massless scalar in DS at late times. Remarkably, this fully quantum system loses phase information and exhibits semiclassical dynamics in the leading approximation. Recasting this as a “resummation of time,” we wish understand whether the distributions that result can be thought of as an attractive UV fixed point of a theory living on a spacelike slice of DS.

Andrew Zentner (Pittsburgh) Tue. February 7th, 2017
11:00 am-12:00 pm

The Power-Law Galaxy Correlation Function

For nearly 40 years, the galaxy-galaxy correlation function has been used to characterize the distribution of galaxies on the sky. In addition, the galaxy correlation function has been recognized as very nearly power-law like despite the fact that it is measured over a wide range of scales. In particular, the galaxy correlation function has been measured on very large scales (~30 Mpc), on which density fluctuations are mild and perturbative approaches are appropriate, as well as very small scales (~0.1 Mpc), on which the evolution of the density field of the universe is quite nonlinear.

Kurt Hinterbichler (CWRU) Tue. January 31st, 2017
11:00 am-12:00 pm

Partially Massless Higher-Spin Gauge Theory

The higher spin theories of Vasiliev are gauge theories that contain towers of massless particles of all spins, and are thought to be UV complete quantum theories that include gravity, describing physics at energies much higher than the Planck scale. We discuss Vasiliev-like theories that include towers of massless and partially massless fields. These massive towers can be thought of as partially Higgs-ed versions of Vasiliev theory. The theory is a fully non-linear theory which contains partially massless modes, is expected to be UV complete, includes gravity, and can live on dS as well as AdS.

Lucile Savary (MIT) — Michelson Postdoctoral Prize Lecturer Tue. January 24th, 2017
11:00 am-12:00 pm

Quantum Spin Ice

Recent work has highlighted remarkable effects of classical thermal fluctuations in the dipolar spin ice compounds, such as “artificial magnetostatics.” In this talk, I will address the effects of terms which induce quantum dynamics in a range of models close to the classical spin ice point. Specifically, I will focus on Coulombic quantum spin liquid states, in which a highly entangled massive superposition of spin ice states is formed, allowing for dramatic quantum effects: emergent quantum electrodynamics and its associated emergent electric and magnetic monopoles. I will also discuss how random disorder alone may give rise to both a quantum spin liquid and a Griffiths Coulombic liquid–a Bose glass-like phase.

Lucile Savary (MIT) — Michelson Postdoctoral Prize Lecturer Mon. January 23rd, 2017
4:15 pm-5:15 pm

A New Type of Quantum Criticality in the Pyrochlore Iridates

The search for truly quantum phases of matter is one of the center pieces of modern research in condensed matter physics. Quantum spin liquids are exemplars of such phases. They may be considered “quantum disordered” ground states of spin systems, in which zero point fluctuations are so strong that they prevent conventional magnetic long range order. More interestingly, quantum spin liquids are prototypical examples of ground states with massive many-body entanglement, of a degree sufficient to render these states distinct phases of matter. Their highly entangled nature imbues quantum spin liquids with unique physical aspects,

Claire Zukowski (Columbia U.) Tue. January 17th, 2017
11:00 am-12:00 pm

Emergent de Sitter Spaces from Entanglement Entropy

A theory of gravity can be holographically “emergent” from a field theory in one lower dimension. In most known cases, the gravitational theory lives in an asymptotically anti- de Sitter spacetime with very different properties from our own de Sitter universe. I will introduce a second emergent “auxiliary” spacetime constructed from the entanglement entropy of subregions in the field theory. In 2d, this auxiliary space is either a de Sitter spacetime or its various identifications. The modular Hamiltonian, which encodes information about the entanglement properties of a state in the field theory,

Beatrice Bonga (Penn State) Tue. December 6th, 2016
11:00 am-12:00 pm

The closed universe and the CMB
Cosmic microwave background (CMB) observations put strong constraints on the spatial curvature via estimation of the parameter $\Omega_k$. This is done assuming a nearly scale-invariant primordial power spectrum. However, we found that the inflationary dynamics is modified due to the presence of spatial curvature leading to corrections to the primordial power spectrum. When evolved to the surface of last scattering, the resulting temperature anisotropy spectrum shows deficit of power at low multipoles ($\ell<20$). This may partially explain the observed $3 \sigma$ anomaly of power suppression for $\ell <30$. Since the curvature effects are limited to low multipoles,

Yi-Zen Chu (University of Minnesota, Duluth) Tue. November 29th, 2016
11:00 am-12:00 pm

Causal Structure Of Gravitational Waves In Cosmology

Despite being associated with particles of zero rest mass, electromagnetic and gravitational waves do not travel solely on the null cone in generic curved spacetimes. (That is, light does not always propagate on the light cone.) This inside-the-null-cone propagation of waves is known as the tail effect, and may have consequences for the quantitative prediction of gravitational waves from both in-spiraling binary compact stars/black holes and “Extreme-Mass-Ratio” systems. The latter consists of compact objects orbiting, and subsequently plunging into, the horizons of super-massive black holes astronomers now believe reside at the center of many (if not all) galaxies —

Daniel Winklehner (MIT) Tue. November 22nd, 2016
11:00 am-12:00 pm

On the development and applications of high-intensity cyclotrons in neutrino physics and energy research

The cyclotron is one of, if not the, most versatile particle accelerator ever conceived. Based on the (then revolutionary) principle of cyclic acceleration using RF frequency alternating voltage on a so-called dee, while particles are forced into circular orbits by a strong vertical magnetic field, many varieties have been developed in the 84 years since their invention by Lawrence in 1932. The fact that they are still around and oftentimes in a form that has been proposed many years ago is a testimony to their robustness and versatility.

Austin Joyce (Kavli Institute for Cosmological Physics, Chicago) Tue. November 15th, 2016
11:00 am-12:00 pm

Soft limits, asymptotic symmetries, and inflation in Flatland

There has been much recent interest in soft limits, both of flat space S-Matrix elements and of cosmological correlation functions. I will discuss the physics probed by soft limits in cosmology and explore the connection between cosmological soft theorems and asymptotic symmetries. These ideas will be illustrated by a simple example: inflation in 2+1 dimensions.

Rachel Rosen (Columbia University) Tue. November 8th, 2016
11:00 am-12:00 pm

Non-Singular Black Holes in Massive Gravity

When starting with a static, spherically-symmetric ansatz, there are currently two types of black hole solutions in massive gravity: (i) exact Schwarzschild solutions which exhibit no Yukawa suppression at large distances and (ii) solutions which contain coordinate-invariant singularities at the horizon.  In this talk, I will present new black hole solutions which have a nonsingular horizon and can potentially be matched to Yukawa asymptotics at large distances.  These solutions recover Schwarzschild black holes in the massless limit and are thus observationally viable.”

Tao Han (University of Pittsburgh) Fri. November 4th, 2016
11:00 am-12:00 pm

Splitting and showering in the electroweak sector

We derive the splitting functions for the Standard Model electroweak sector at high energies, including the fermions, massive gauge bosons and the Higgs boson. We study the class of functions with the “ultra-collinear” behavior that is a consequence of the electroweak symmetry breaking. We stress the leading-order corrections to the “Goldstone-boson Equivalence Theorem”. We propose a novel gauge, dubbed the “Goldstone Equivalence Gauge” that practically as well as conceptually disentangles the effects from the Goldstone bosons and the gauge fields. We also demonstrate a practical scheme for multiple electroweak boson production via showering at high energies.

Sean Bryan (Arizona State University) Tue. October 18th, 2016
11:00 am-12:00 pm

Cosmology with Millimeter Wave LEKIDs: CMB, Spectroscopy, and Imaging with TolTEC

Millimeter-wave cameras offer a unique window on the history and dynamics of the universe. Observations of CMB polarization are setting new constraints on cosmic inflation and gravitational lensing. Imaging and spectroscopy in millimeter waves measures individual galaxies through their bolometric flux as well as C+/CO line strengths. In this talk, I will discuss aluminum LEKID detectors that can be used for all of these applications. The feed structures are directly machined in metal, and the detectors are made with a single-layer process. Lab measurements show that the 150 GHz dual-polarization detectors have photon-noise limited sensitivity,

Stacy McGaugh (CWRU Astronomy) [note time] Tue. October 11th, 2016
11:00 am-12:00 pm

*Note that the seminar may be pushed back to 11:30-12:30.

The Radial Acceleration Relation in Rotationally Supported Galaxies

We report a correlation between the radial acceleration traced by rotation curves and that predicted by the observed distribution of baryons. The same relation is followed by 2693 points in 153 galaxies with very different morphologies, masses, sizes, and gas fractions. The correlation persists even when dark matter dominates. Consequently, the dark matter contribution is fully specified by that of the baryons. The observed scatter is small and largely dominated by observational uncertainties. This radial acceleration relation is tantamount to a natural law for rotating galaxies.
Henriette Elvang (University of Michigan) Tue. September 20th, 2016
11:00 am-12:00 pm

Scattering amplitudes and soft theorems

I will give a pedagogical introduction to the spinor helicity formalism which provides a very efficient tool for studies of on-shell scattering amplitudes in 4 dimensions. The power of this formalism will be demonstrated in a new analysis of soft photon and soft graviton theorems.

Bob Brown (CWRU) Tue. September 13th, 2016
11:00 am-12:00 pm

Understanding Color-Kinematics Duality with a New Symmetry: From Radiation Zeros to BCJ

I discuss a new set of symmetries obeyed by tree-level gauge-theory amplitudes involving at least one gluon. The symmetry acts as a momentum-dependent shift on the color factors of the amplitude. Using our previous development of radiation vertex expansions, we prove the invariance under this color-factor shift of the n -gluon amplitude, and in fact for any amplitudes involving at least one massless gauge boson and any number of massless or massive particles in arbitrary representations of the gauge group with spin zero,

Bryan Lynn (CWRU and University College London) Tue. September 6th, 2016
11:00 am-12:00 pm

Raymond Stora’s last work

Excursion Sets, Peaks and Other Creatures: Improved Analytical Models of LSS – Marcello Musso Tue. May 3rd, 2016
11:30 am-12:30 pm

I will present recent developments in analytical methods to predict abundance, clustering, velocities and bias of Dark Matter halos. In the standard analytical approach, halos are identified either with sufficiently high peaks of the initial matter density field, or with the largest spheres enclosing a sufficiently high density. I will revise the physical assumptions leading to this standard picture, and show how a careful statistical implementation of the model of collapse (even in the simple spherically symmetric case) leads to a surprisingly rich structure. This allows to make simple – yet remarkably accurate – analytical predictions for halo statistics, a necessary ingredient on the road to precision cosmology.

Do We Understand the Universe? – Raul Jimenez Tue. April 26th, 2016
11:30 am-12:30 pm

Observations of the cosmos provide a valuable tool to study the fundamental laws of nature. The future generation of astronomical surveys will provide data for a sizeable fraction of the observable sky. This rich data set should provide the means to answer fundamental questions: what are the laws of physics at high energies in the Early Universe? What is the nature of neutrinos? What is dark matter? What is dark energy? Why are there baryons at all? In this talk I will review the current status, provide a roadmap for future prospects and discuss in detail how we might approach the task of extracting information from the sky to answer the above questions.

New Directions in Bouncing Cosmologies – Anna M. Ijjas Tue. April 19th, 2016
11:30 am-12:30 pm

In this talk, I will discuss novel ideas to smooth and flatten the universe and generate nearly scale-invariant perturbations during a contracting phase that precedes a cosmological bounce. I will also present some recent work on the possibility of having well-behaved non-singular bounces.

Beyond Precision Cosmology – Licia Verde Tue. April 5th, 2016
11:30 am-12:30 pm

The avalanche of data over the past 10-20 years has propelled cosmology into the “precision era”. The next challenge cosmology has to meet is to enter the era of accuracy. Because of the intrinsic nature of studying the Cosmos and the sheer amount of data available and coming, the only way to meet these challenges is by developing suitable and specific statistical techniques. The road from precision Cosmology to accurate Cosmology goes through statistical Cosmology. I will outline some open challenges and discuss some specific examples.

New Approaches to Dark Matter – Justin Khoury Tue. March 29th, 2016
11:30 am-12:30 pm

In this talk I will discuss a novel theory of superfluid dark matter. The scenario matches the predictions of the LambdaCDM model on cosmological scales while simultaneously reproducing the MOdified Newtonian Dynamics (MOND) empirical success on galactic scales. The dark matter and MOND components have a common origin, as different phases of a single underlying substance. This is achieved through the rich and well-studied physics of superfluidity. The framework naturally distinguishes between galaxies (where MOND is successful) and galaxy clusters (where MOND is not): due to the higher velocity dispersion in clusters, and correspondingly higher temperature, the DM in clusters is either in a mixture of superfluid and normal phases,

Calibration of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) Detectors – Madeline Wade Tue. March 22nd, 2016
11:30 am-12:30 pm

Calibration is the critical link between the LIGO detectors and searches for gravitational-wave signals in LIGO data. The LIGO calibration effort involves constructing the external strain incident on each LIGO detector from the digitized readout of the LIGO photodetectors. The essential steps in calibration are the development of accurate models of the LIGO detectors, the digitization of these models, and the application of the calibration models to construct the external strain. The Advanced LIGO era has brought new complexities in accurately modeling the LIGO detectors as well as the challenge of producing calibrated external strain data in low-latency. This talk will give an overview of the Advanced LIGO calibration procedure,

New Probes of Large-scale CMB Anomalies – Simone Aiola Tue. March 15th, 2016
11:30 am-12:30 pm

Inflation prescribes a homogenous and isotropic universe on large scales, and it generates density fluctuations which are expected to be spatially correlated over the whole Hubble volume. Such fundamental predictions have been tested with current Cosmic Microwave Background (CMB) data and found to be in tension with our — remarkably simple — ΛCDM model. Is it just a random fluke or a fundamental issue with the present model? In this talk, I will present new possibilities of using CMB polarization as a probe of the measured suppression of the large-scale temperature correlation function. I will also discuss the viability of using this new technique with present and upcoming data.

Joining Forces Against the Dark Side of the Universe: The Cosmic Microwave Background and the Large Scale Structure – Shirley Ho Fri. March 4th, 2016
12:30 pm-1:30 pm

Despite tremendous recent progress, gaps remain in our knowledge of our understanding of the Universe. For example, we have yet pinned down the properties of dark energy, nor have we confirmed Einstein’s theory of Gravity at the largest scales. Current and upcoming large sky surveys of the cosmic microwave background, large scale structure in galaxies, quasars, lyman-alpha forest and 21cm presents us with the best opportunity to understand various mysterious properties of the Universe and its underlying principles. I will review recent results from the Baryon Oscillations Spectroscopic Survey (BOSS). These results have demonstrated the feasibility of high precision Baryon Acoustic Oscillation (BAO) measurement,

Testing Early Universe Physics with Upcoming Observations – Emanuela Dimastrogiovanni Wed. February 10th, 2016
12:30 pm-1:30 pm

Cosmology has seen tremendous progress thanks to precision measurements and is bound to greatly benefit from upcoming Large Scale Structure and Cosmic Microwave Background data. I will point out a number of interesting directions. In particular, I discuss how the microphysics of inflation may be tested in galaxy surveys through “fossil” signatures originating from squeezed primordial correlations. I further elaborate on the constraining power of CMB spectral distortions on small-scale cosmological fluctuations and on particle decays in the very early Universe in relation to reheating. I also describe some of the possible constraints on inflation and reheating from future B-mode observations.

New Paradigm for Physics Beyond the Standard Model – Pavel Fileviez Perez Tue. February 9th, 2016
11:30 am-12:30 pm

The great desert hypothesis in particle physics defines the relation between the electroweak scale and the high scale where an unified theory could describes physics. In this talk we review the desert hypothesis and discuss the main experimental constraints from rare decays. We present a new class of theories for the TeV scale where the desert hypothesis is not needed. In this context one predicts the existence of new particles with baryon and lepton numbers called lepto-baryons. The implications for cosmology, collider experiments and the unification of forces are discussed.

Cosmology from the Megaparsec to the Micron – Amol Upadhye Fri. February 5th, 2016
12:30 pm-1:30 pm

Two major challenges for cosmology over the next decade are to characterize the dark energy responsible for the cosmic acceleration and to weigh the neutrinos, the only Standard Model particles whose masses are not yet known. Part I of the presentation describes my ongoing work to understand the effects of massive neutrinos and evolving dark energy on the formation of large-scale structure. I include both effects in a redshift-space generalization of Time-RG perturbation theory, and establish its validity through comparison to N-body simulations. In Part II I discuss my previous work using stars and laboratory experiments to search for couplings between dark energy and Standard Model particles.

Massive and Partially Massless Gravity and Higher spins – Kurt Hinterbichler Tue. February 2nd, 2016
11:30 am-12:30 pm

On de Sitter space, there exists a special value for the mass of a graviton for which the linear theory propagates 4 rather than 5 degrees of freedom, known as a partially massless graviton. If a satisfactory non-linear version of the theory can be found and coupled to known matter, it would have interesting properties and could solve the cosmological constant problem. I will review attempts at constructing such a theory and some no-go’s, and will describe a Vasiliev-like theory containing a tower of partially massless higher spins.

Testing Eternal Inflation – Matthew Johnson Tue. December 8th, 2015
11:30 am-12:30 pm

The theory of eternal inflation in an inflaton potential with multiple vacua predicts that our universe is one of many bubble universes nucleating and growing inside an ever-expanding false vacuum. The collision of our bubble with another could provide an important observational signature to test this scenario. In this talk I will summarize recent work providing a quantitative connection between the scalar field lagrangian underlying eternal inflation and the observational signature of bubble collisions. I will also summarize existing constraints and forecasts for future searches using CMB and LSS, as well as discuss the general relevance of this work for assessing fine-tuning problems in inflationary cosmology.

Bigravity: Dead or Alive? – Adam Solomon Tue. December 1st, 2015
11:30 am-12:30 pm

Spurred in large part by the discovery of the accelerating universe, recent years have seen tremendous advances in our understanding of alternatives to general relativity, particularly in the large-distance and low-curvature régimes. Looming large in this field is the recent development of a ghost-free, nonlinear theory of massive gravity and multimetric gravity (or equivalently, theories of interacting gravitons), which had proven elusive for the better part of seven decades. Nevertheless, both massive gravity and its generalization to a bimetric theory have run into potentially-deadly problems in the search for viable, self-accelerated cosmologies. I will summarize some of these issues, and then discuss possible ways out.

Bi-gravity from DGP Two-brane Model – Yasuho Yamashita Wed. October 28th, 2015
12:30 pm-1:30 pm

We discuss whether or not bigravity theory can be embedded into the braneworld setup. As a candidate, we consider Dvali-Gabadadze-Porrati two-brane model. We will show that we can construct a ghost free model whose low energy spectrum is composed of a massless graviton and a massive graviton with a small mass, fixing the brane separation with the Goldberger-Wise radion stabilization. We also show that there is two branches: the normal branch is stable and the self-accelerating branch is inevitably unstable, and discuss the condition for the normal branch. Next, we consider DGP two-brane model without the radion stabilization to discuss how the ghost free bigravity coupled with a single scalar field can be derived from a braneworld setup.

The Instability of de Sitter Space and Dynamical Dark Energy: Massless Degrees of Freedom from the Conformal Anomaly in Cosmology – Emil Mottola Tue. October 27th, 2015
11:30 am-12:30 pm

Global de Sitter space is unstable to particle creation, even for a massive free field theory with no self-interactions. The Bunch-Davies state is a definite phase coherent superposition of particle and anti-particle solutions in both the asymptotic past and future, and therefore is not a true vacuum state. In the closely related case of particle creation by a constant, uniform electric field, a time symmetric state analogous to the de Sitter invariant one is constructed, which is also not a stable vacuum state. The conformal anomaly plays a decisive role in the growth of perturbations and de Sitter symmetry breaking.

Perspectives on WIMP Dark Matter – Pearl Sandick Tue. October 13th, 2015
11:30 am-12:30 pm

The question of the identity of dark matter remains one of the most important outstanding puzzles in modern physics. Weakly Interacting Massive Particles (WIMPs) have long been the frontrunner dark matter candidate, with the supersymmetric neutralino serving as the canonical WIMP. In this talk, I’ll discuss recent results relevant to the search for dark matter, supersymmetric and otherwise, and highlight the spectrum of theoretical and phenomenological approaches to its study. From fundamental constructions to simplified models and effective theories, each approach plays a specific role in furthering our understanding and allowing us to evaluate the prospects for discovery of dark matter.

The Standard Model of Particle Physics via Non-Commutative Geometry – Latham Boyle Fri. October 9th, 2015
12:30 pm-1:30 pm

I will introduce Connes’ notion of non-commutative geometry, and explain how it offers a novel geometric perspective on certain otherwise unexplained features of the standard model of particle physics, and a more restrictive framework than effective field theory for exploring physics beyond the standard model. I will also explain the main ideas behind a new reformulation of NCG which has certain key mathematical and physical advantages over Connes’ traditional “spectral triple” formulation. In this reformulation, the traditional NCG axioms are considerably simplified and unified; a number of problematic issues in the traditional NCG construction of the standard model are fixed;

An Anisotropic Universe Due to Dimension-changing False Vacuum Decay – James Scargill Tue. September 29th, 2015
11:30 am-12:30 pm

In this talk I will consider the observational consequences of models of inflation after false vacuum decay in which the parent vacuum has a smaller number of large dimensions than our current vacuum. After introducing and briefly discussing in general the topic of inflation after false vacuum, I will then explain how such events can occur which change the number of large dimensions and lead to an anisotropic universe. The effects on the CMB of anisotropy at late times might be expected to render irrelevant the effects of primordial anisotropy, however after showing how to properly deal with the latter I will demonstrate how for the tensor perturbation modes the primordial effects are much larger than expected and can in fact be dominant.

Prospects for Measuring the Neutron-star Equation of State with Advanced Gravitational-wave Detectors – Leslie Wade Tue. September 22nd, 2015
11:30 am-12:30 pm

It is widely anticipated that the first direct detections of gravitational waves will be made by advanced gravitational-wave detectors, such as the two Laser Interferometer Gravitational-wave Observatories (LIGO) and the Virgo interferometer. Arguably the most important source for ground-based interferometers are coalescing binary neutron stars. Following the detection of such a system, a more detailed followup analysis will seek to measure certain properties of the component neutron stars, such as their masses and/or spin configurations. In particular, it has been shown that the gravitational waves emitted by binary neutron stars carry information about the neutron-star equation of state. In this talk,

Gravitational Signals from Noise in the Hubble Diagram – Edward Macaulay Tue. May 5th, 2015
11:30 am-12:30 pm

Understanding the nature of the dark universe requires precise measurements of the background expansion history, and also the growth rate of density fluctuations. In this talk, I’ll consider both regimes with supernova lensing for the OzDES spectroscopic survey – which is measuring the redshifts of hundreds of supernova and thousands of galaxies identified by the Dark Energy Survey. I’ll start by reviewing the more established method of growth rate measurements with Redshift Space Distortions, and discuss possible tension between RSDs and expectations from Planck CMB measurements. I’ll then consider how OzDES can place novel constraints on the growth rate and amplitude of density fluctuations by correlating noise in the supernova Hubble diagram with the gravitational effects of lensing and peculiar velocities expected from the observed density field.

The Race for the Highest Energy Neutrinos in the Universe – Patrick Allison Tue. April 7th, 2015
11:30 am-12:30 pm

In 1969, Berezinsky and Zatsepin predicted a flux of ultra-high energy (greater than 1 EeV) neutrinos due to cosmic ray interactions with the cosmic microwave background. These ‘cosmogenic’ BZ neutrinos are virtually “guaranteed” – barring extreme changes in either fundamental physics or our understanding of the source of cosmic rays, these neutrinos must exist. Detecting these neutrinos is extremely challenging, due to their incredibly low flux – however, recent experiments are approaching the sensitivity needed to finally make a detection. Here, I will talk about several of these existing and upcoming experiments, including the ANITA and EVA balloon-borne detectors, and the ARA experiment,

Macro Dark Matter – David Jacobs Tue. March 31st, 2015
11:30 am-12:30 pm

Dark matter is a vital component of the current best model of our universe, Lambda-CDM. There are leading candidates for what the dark matter could be (e.g. weakly-interacting massive particles, or axions), but no compelling observational or experimental evidence exists to support these particular candidates, nor any beyond-the-Standard-Model physics that might produce such candidates. This suggests that other dark matter candidates, including ones that might arise in the Standard Model, should receive increased attention. I will discuss the general class of dark matter candidates with characteristic masses and interaction cross-sections characterized in units of grams and square centimeters, respectively —

Wave Turbulence in Preheating – Henrique de Oliveira Tue. March 24th, 2015
11:30 am-12:30 pm

We have studied the nonlinear preheating dynamics of several inflationary models. They include nonminimally coupled scalar fields and two-fields models. It is well established that after a linear stage of preheating characterized by the parametric resonance, the nonlinear dynamics becomes relevant driving the system towards turbulence. Wave turbulence is the appropriated description of this phase since the matter contents are fields instead of usual fluids. Turbulence develops due to the nonlinear interations of waves, here represented by the small inhomogeneities of the scalar fields. We present relevant aspects of wave turbulence and presented the effective equation of state at the thermalize phase.

Mapping New Physics with the Cosmic Microwave Background – Jeff McMahon Mon. February 23rd, 2015
11:30 am-12:30 pm

The Cosmic Microwave Background (CMB) is the afterglow of the big bang and the oldest light in the universe that can be observed. Faint signals in the pattern of the CMB provide information about the physics that govern the very early universe and the growth of large scale structure. Thus, precision measurements of the CMB provide unique views on ultra high energy physics (inflation); pressing mysteries including dark energy and dark matter; and traditional particle physics questions such as the sum of the neutrino masses. In this talk I present the state of the CMB field and highlight the Atacama Cosmology Telescope Polarimeter (ACTPol) and it successor Advanced ACTPol (AdvACT).

Optical Frequency Combs and Precision Spectroscopy – Jason Stalnaker Tue. February 17th, 2015
11:30 am-12:30 pm

Atomic spectroscopy has a long history of providing tests of fundamental physics. This tradition continues as the precision and accuracy of spectroscopic techniques improve. I will discuss the impact that the development of stabilized optical frequency combs has had on precision spectroscopy and describe an ongoing effort to study the atomic spectra of lithium at Oberlin College.

Numerical Relativity in Spherical Polar Coordinates – Thomas W. Baumgarte Thu. February 12th, 2015
11:30 am-12:30 pm

Numerical relativity simulations have made dramatic advances in recent years. Most of these simulations adopt Cartesian coordinates, which have some very useful properties for many types of applications. Spherical polar coordinates, on the other hand, have significant advantages for others. Until recently, the new coordinate singularities in spherical polar coordinates have hampered the development of numerical relativity codes adopting such coordinates, at least in the absence of symmetry assumptions. With a combination of different techniques – a reference-metric formulation of the relevant equations, a proper rescaling of all tensorial quantities, and a partially-implicit Runge-Kutta method – we have been able to solve these problems.

Is Clustering Dark Energy Non-linear? The AP Resummation Approach – Stefano Anselmi Tue. February 3rd, 2015
11:30 am-12:30 pm

In order to gain insights on the mysterious component driving the acceleration of the Universe the future surveys will measure with unprecedent precision the density power spectrum in the non-linear range of scales and redshifts. On the theoretical hand those non-linearities require a comparable computational level. This is a tremendous effort that see deployed numerical (N-body), semi-analytical and analytical investigations. I this context I will present a powerful analytical resummation scheme first developed for LCDM and very recently extended to the Clustering Quintessence scenario, i.e. quintessence models with vanishing speed of sound. The approach I will expose allows predictions at few percent level beyond the Baryon Acoustic Oscillations range of scales,

Sterile Plus Active Neutrinos and Neutrino Oscillations – Leonard Kisslinger Mon. January 26th, 2015
12:30 pm-1:30 pm

The talk will be based on recent neutrino oscillation experiments that have determined that there is almost certainly a sterile neutrino, with an estimate of the mixing angle.

New Accelerators for Neutrino Physics – Matt Toups Tue. January 20th, 2015
11:30 am-12:30 pm

DAEδALUS is a proposed phased neutrino experiment, whose ultimate aim is to search for evidence of CP violation in the neutrino sector. The experiment will consist of several accelerator-based modules that produce decay-at-rest neutrino beams located at three different distances from a single, large underground neutrino detector. Each of these modules will make use of a pair of low-cost, high power cyclotrons to accelerate an H2+ beam initially up to 60 MeV with a compact injector cyclotron and then ultimately up to 800 MeV with a separated sector super-conducting cyclotron. These new low-cost, high power cyclotrons are motivated by industry needs and also open up new possibilities for searches for physics beyond the standard model with neutrinos.

The Universe as a Cosmic String – Florian Niedermann Tue. November 25th, 2014
11:30 am-12:30 pm

We are investigating modifications of general relativity that are operative at the largest observable scales. In this context, we are investigating the model of brane induced gravity in 6D, a higher dimensional generalization of the DGP model. As opposed to different claims in the literature, we have proven the quantum stability of the theory in a weakly coupling regime on a Minkowski background. In particular, we have shown that the Hamiltonian of the linear theory is bounded from below. This result opened a new window of opportunity for consistent modified Friedmann cosmologies. In our recent work it is shown that a brane with FRW symmetries necessarily acts as a source of cylindrically symmetric gravitational waves,

Imprints of the Standard Model in the Sky? – Daniel G. Figueroa Tue. November 18th, 2014
11:30 am-12:30 pm

The existence of the Standard Model (SM) Higgs implies that a gravitational wave (GW) background is generated by the decay products of the Higgs, soon after the end of inflation. Theoretically, all Yukawa and SU(2)L gauge couplings of the SM are imprinted as features in the GW spectrum. However, in practice, the signal from the most strongly coupled species dominate, rendering inaccesible the information on the other species. This background could be used for inferring properties of particle physics, including beyond the SM, at energies way above the reach of LHC. To measure this background, however, new high frequency GW detection technology is required.

New Ideas for Dark Energy and Also for Dust Discrimination in B-mode Maps – Marc Kamionkowski Fri. November 14th, 2014
12:30 pm-1:30 pm
Intergalactic Magnetic Fields – Tanmay Vachaspati Tue. November 11th, 2014
11:30 am-12:30 pm

I will describe theoretical motivation for the existence of parity violating (helical) intergalactic magnetic fields and recent and growing observational evidence for such fields.

Peaks and Troughs in Large Scale Structure – Ravi K. Sheth Tue. November 4th, 2014
11:30 am-12:30 pm

I will reiew recent and substantial progress in modeling the cosmic web. This progress, which results from merging two different and decades old literature streams, leads to a number of new and interesting insights about how the biased tracers we will observe in the next generation of large scale structure datasets can better constrain cosmological models.

High Precision Cosmology with BAO Surveys: BOSS and Future 21cm BAO Surveys – Hee-Jong Seo Fri. October 24th, 2014
12:30 pm-1:30 pm

The large scale structure of matter and galaxies contains important information on the evolution of the Universe. Baryon acoustic oscillations (BAO), which is one of the most promising large scale features, can provide an excellent standard ruler that enables us to measure the cosmological distance scales, and therefore dark energy properties. I would like to first discuss the ongoing joint analysis of BOSS galaxy and lya BAO results and, second, future 21cm BAO surveys focused on the effect of foregrounds.

The Shape of the Electron, and Why It Matters – Amar Vutha Tue. October 14th, 2014
11:30 am-12:30 pm

The universe, or at least the 5% of it that we understand, is described rather well by the Standard Model of particle physics. Yet even this non-dark sector of the universe conceals a great mystery: // where has all the anti-matter gone? // In this lecture, I will describe the problem and the best solution that we have for it. One of the crucial ingredients of that solution is the prediction of new sources of time-reversal violation. The most sensitive probe of such time-reversal violation is, oddly enough, to be found in small asymmetries in the shape of the electron’s charge distribution.

Precision Cosmology with Galaxy Surveys: Understanding Intrinsic Alignments and Redshift-space Distortions – Jonathan A. Blazek Fri. October 10th, 2014
12:30 pm-1:30 pm

Galaxy imaging and redshift surveys, designed to measure gravitational lensing and galaxy clustering, remain the most powerful probes of large-scale structure. Such surveys constitute a significant fraction of current and next-generation projects in the cosmology community (e.g. DES, HSC, LSST, eBOSS, DESI, EUCLID, WFIRST). The statistical power of these experiments requires significantly improved understanding of astrophysical and observational effects. In this talk, I will focus on two important astrophysical processes which contribute systematic uncertainty but also contain a potential wealth of information. First, correlations in the intrinsic shapes and orientations of galaxies, termed “intrinsic alignments” (IA), are an important systematic in weak lensing.

Healthy Theories Beyond Horndeski – Jerome Gleyzes Wed. September 3rd, 2014
11:30 am-12:30 pm

In search for a candidate that could explain the current acceleration of the Universe, a lot of attention has been given recently to Galileon theories, or in their generalized form, Horndeski theories. They are interesting as they represent the most general scalar tensor theories that do not lead to equations of motion containing more than two derivatives. This restriction is generally thought to be of great importance, as generically, higher order derivatives lead to ghost instabilities. I will present a new class of scalar tensor theories that are broader than Horndeski and, as such, do bring higher order derivatives. However,

Interacting Spin-2 Fields – Johannes Noller Tue. September 2nd, 2014
11:30 am-12:30 pm

In this talk I will discuss some recent progress in our understanding of the spin-2 sector, focussing on theories with two or more dynamical such fields. In particular I will highlight the existence of several dualities in such models (generalisations of `Galileon dualities’), their decoupling limit phenomenology as well as the form of their interactions with other matter fields.

Recent Progress in Large-Scale Structure – Roman Scoccimarro Fri. May 9th, 2014
11:00 am-12:00 pm

I will discuss recent progress in the understanding of how to model galaxy clustering. While recent analyses have focussed on the baryon acoustic oscillations as a probe of cosmology, galaxy redshift surveys contain a lot more information than the acoustic scale. In extracting this additional information three main issues need to be well understood: nonlinear evolution of matter fluctuations, galaxy bias and redshift-space distortions. I will present recent progress in modeling these three effects that pave the way to constraining cosmology and galaxy formation with increased precision.

Atom Interferometry Fundamentals and its Applications in Space Science – Babak Saif Tue. May 6th, 2014
11:30 am-12:30 pm
Shape of the Universe – Daniel Müller Tue. April 29th, 2014
11:30 am-12:30 pm

The most recent observations indicate that the Universe is isotropic, with a small spatial curvature, which can be either positive, negative or zero. As is well known, Einstein’s theory of gravitation restricts the spatially isotropic sections of space time to be locally S^3, H^3 or E^3, respectively. Thus, the topology of the Universe is only partly determined. On the other hand there are a few effects which occur for non trivial topology. In this talk, we will give a brief discussion of some of these, in particular of the Casimir effect which should have been important in the primordial stages of the Universe.

Testing Gravity via Lunar Laser Ranging – Tom Murphy Tue. April 22nd, 2014
11:30 am-12:30 pm

Forty years ago, Apollo astronauts placed the first of several retroreflector arrays on the moon. Laser range measurements between the earth and the moon have provided some of our best tests to date of general relativity and gravitational phenomenology–including the equivalence principle, the time-rate-of-change of the gravitational constant, the inverse square law, and gravitomagnetism. A new effort called APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation) is now collecting measurements at the unprecidented precision of one millimeter, which will produce order-of-magnitude improvements in a variety of gravitational tests, as well as reveal more detail about the interior structure of the moon.

WIMP physics with direct detection – Annika H. G. Peter Tue. April 8th, 2014
11:30 am-12:30 pm

One of the best-motivated classes of dark-matter candidate is the Weakly-Interacting Massive Particle (WIMP). In this talk, I will discuss WIMPs in the context of direct-detection experiments. First, I will discuss a new signal for WIMP dark matter: gravitational focusing in direct-detection experiments. This effect leads to an energy-dependent phase-shift in the peak direct-detection event rate throughout the year. I will discuss this in light of current putative annual-modulation claims. Second, I will discuss what we can learn about WIMPs in the “early-discovery” days once WIMPs are conclusively found in direct-detection experiments. I will show that what we can learn about WIMPs depends sensitively on the ensemble of experiments that are running at the time of discovery.

Probing Dark Energy Using Growth of Structure: The Role of Simulations – Hao-Yi Wu Tue. April 1st, 2014
11:30 am-12:30 pm

The growth of cosmic structure provides a unique approach for measuring the dynamic evolution of dark energy and distinguishing different models of gravity. In this talk, I will focus on two of the most important methods for measuring the growth of structure: galaxy cluster counts and the redshift-space distortions of galaxy clustering. I will discuss the systematic uncertainties involved in both methods, and how I use numerical simulations to help reducing these systematics and improve our theoretical predictions.

Science with CMB Spectral Distortions: a New Window to Early-Universe Physics – Jens Chluba Tue. March 18th, 2014
11:30 am-12:30 pm

Since COBE/FIRAS we know that the CMB spectrum is extremely close to a perfect blackbody. There are, however, a number of processes in the early Universe that should create spectral distortions at a level that is within reach of present day technology. I will give an overview of recent theoretical and experimental developments, explaining why future measurements of the CMB spectrum will open up an unexplored window to early-universe and particle physics, with possible non-standard surprises but also guaranteed signals awaiting us.

The Marvelous Success of the Standard Model of Cosmology – Lloyd Knox Wed. February 26th, 2014
12:30 pm-1:30 pm

The standard model of cosmology has been remarkably successful in its predictions for current data given earlier data. One can react with sadness for the lack of evidence for new physics, chase marginal anomalies, or marvel at the success and soldier on toward better measurements knowing new physics may be just around the corner. In this talk I will reveal some of the inner workings of this success in order to communicate why I find it marvelous. For example, for the predictions to agree with cosmic microwave background (CMB) data we need, at very high statistical significance, a cosmic neutrino background,

21cm Cosmology – Ue-Li Pen Tue. February 18th, 2014
11:30 am-12:30 pm

I present recent developments in a new window to map the large scale structure of the universe through intensity mapping using the collective unresolved emission of cosmic hydrogen 21cm emission. Initial maps have been made with various existing telescopes, and an ambitious survey, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is under construction. Future potential science targets include precision measurements of dark energy, neutrino masses, and possibly gravitational waves.

Cosmology and Systematics of Multi-wavelength Galaxy Cluster Observables – Tomasz Biesiadzinski Tue. February 11th, 2014
11:30 am-12:30 pm

The current concordance lCDM cosmological model describes a universe where cold dark matter seeds structure formation and a cosmological constant drives its accelerated expansion. Precise measurements of various astronomical observables allow us to test this model and any deviations, if found, may lead to an improved cosmological theory. Ongoing and planned large scale surveys of the skies have the power to study the lCDM model. However the data sets they generate will be dominated by complex systematic uncertainties. One probe of cosmological parameters, the evolution of clusters of galaxies, has the power to differentiate simple models of dark energy, like the cosmological constant,

Quantum-Limited Superconducting Detectors and Amplifiers for Cosmology – Philip Mauskopf Fri. February 7th, 2014
12:30 pm-1:30 pm
21-cm Intensity Mapping – Jeffrey Peterson Tue. January 28th, 2014
11:30 am-12:30 pm
Supersymmetry, Non-thermal Dark Matter and Precision Cosmology Tue. December 3rd, 2013
11:30 am-12:30 pm

Within the Minimal Supersymmetric Standard Model (MSSM), LHC bounds suggest that scalar superpartner masses are far above the electroweak scale. Given a high superpartner mass, nonthermal dark matter is a viable alternative to WIMP dark matter generated via freezeout. In the presence of moduli fields nonthermal dark matter production is associated with a long matter dominated phase, modifying the spectral index and primordial tensor amplitude relative to those in a thermalized primordial universe. Nonthermal dark matter can have a higher self-interaction cross-section than its thermal counterpart, enhancing astrophysical bounds on its annihilation signals. I will review recent progress in this program,

Cosmic Bandits: Exploration vs. Exploitation in Cosmological Surveys – Ely Kovetz Tue. November 26th, 2013
11:30 am-12:30 pm

Various cosmological observations consist of prolonged integrations over small patches of sky. These include searches for B-modes in the CMB, the power spectrum of 21-cm fluctuations during the epoch of reionization and deep-field imaging by telescopes such as HST/JWST, among others. However, since these measurements are hindered by spatially-varying foreground noise, the observational sensitivity can be improved considerably by finding the region of sky cleanest of foregrounds. The best strategy thus involves a tradeoff between exploration (to find lower-foreground patches) and exploitation (through prolonged integration). But how to balance this tradeoff efficiently? This problem is akin to the multi-armed bandit (MAB) problem in probability theory,

Turning trajectories in multi-field inflation – Krzysztof Turzyński Tue. November 19th, 2013
11:30 am-12:30 pm

The latest results from the PLANCK collaboration, consistent with the simplest single-field models of slow-roll inflation and with no trace of non-Gaussianity, have extinguished many hopes of seeing specific aspects of New Physics directly in the sky. One may then wonder whether the landscape of allowed inflationary models has been practically reduced to single-field effective theories. I shall argue that the answer is negative and present several inflationary models in which the turn-induced interactions between two scalar fields affect the normalization/running of the power spectrum of curvature perturbations, or smooth out its features (e.g. via particle production), actually driving the power spectrum towards phenomenologically acceptable characteristics.

Lorentz violation in gravity: why, how and where – Diego Blas Mon. November 18th, 2013
3:00 pm-4:00 pm

Recent approaches to quantum gravity question the role of Lorentz invariance as a fundamental symmetry of Nature. This has implications for most of the observables in gravitational physics, also at low-energies. In this talk I will describe recent bounds on deviations from Lorentz invariance in gravity coming from binary pulsar observations and cosmological data.

Non-local quantum effects in cosmology – John Donoghue Tue. November 12th, 2013
11:30 am-12:30 pm

In general relativity, there are non-local quantum effects that come from the propagation of light particles including gravitons. I will review the effective field theory treatment which allows one to identify the reliable parts of the quantum loops. In cosmology, there are then non-local corrections to the FLRW equations. I will present some of the formalism for this and give some exploration of results.

Cosmology from conformal symmetry – Austin Joyce Tue. October 29th, 2013
11:30 am-12:30 pm

We will explore the role that conformal symmetries may play in cosmology. First, we will discuss the symmetries underlying the statistics of the primordial perturbations which seeded the temperature anisotropies of the Cosmic Microwave Background. I will show how symmetry considerations lead us to three broad classes of theories to explain these perturbations: single-field inflation, multi-field inflation, and the conformal mechanism. We will discuss the symmetries in each case and derive their model-independent consequences. Finally, we will examine the possibility of violating the null energy condition with a well-behaved quantum field theory.

Goldstone bosons with spontaneously broken Lorentz symmetry – Riccardo Penco Tue. October 15th, 2013
11:30 am-12:30 pm

In this talk, I will discuss some general properties of effective theories of Goldstone bosons in which Lorentz symmetry is spontaneously broken. I will first introduce an extension of Goldstone theorem to systems with a finite density of charge. This very general setting is potentially applicable to contexts as diverse as early universe cosmology and QCD at finite density. Additionally, I will show how certain effective theories of Goldstones with broken Lorentz symmetry admit UV completions that do not restore any broken symmetry.

Slavnov-Taylor Identities for Primordial Perturbations – Lasha Berezhiani Tue. October 8th, 2013
11:30 am-12:30 pm

I will show that all consistency relations for the primordial perturbations derive from a single, master identity, which follows from the Slavnov-Taylor identity for spatial diffeomorphisms. This master identity is valid at any value of momenta and therefore goes beyond the soft limit. This approach underscores the role of spatial diffeomorphism invariance at the root of cosmological consistency relations. It also offers new insights on the necessary conditions for their validity: a physical contribution to the vertex functional must satisfy certain analyticity properties in the soft limit in order for the consistency relations to hold. For standard inflationary models, this is equivalent to requiring that mode functions have constant growing-mode solutions.

Symmetry Breaking and Galileons – Garrett Goon Wed. October 2nd, 2013
11:30 am-12:30 pm

Galileons, and related theories, have deep connections to spontaneous symmetry breaking. After reviewing the origins of Galileon theories, I motivate their interpretation as Goldstone Bosons and illustrate some of their special technical properties before proceeding to discuss applications and future directions.

CMB Lensing: reconstruction from polarisation & implications for cosmology from cross correlation with galaxies – Ruth Pearson Tue. September 24th, 2013
11:30 am-12:30 pm

CMB Lensing is a probe of the matter distribution between the surface of last scattering and today, which has been measured using CMB temperature data. Signal to noise for lensing reconstruction from CMB polarisation data is expected to be much better, since B modes on small scales should vanish in the absence of lensing. An effect of having data from an incomplete sky is leakage of E mode power in to B mode power. Upcoming data analysis from ground based CMB polarisation instruments must account for this effect. In the first part of my talk I will show results for CMB polarisation lensing reconstruction from small patches of sky,

Making the connection between galaxy voids, dark matter underdensities and theory – Paul Sutter Tue. September 10th, 2013
11:30 am-12:30 pm

TBA

The Universe in a New Light: the First Cosmological Results from the Planck Mission – Bill Jones Tue. April 30th, 2013
2:30 pm-3:30 pm

The precision and accuracy of the recently released Planck data are without precedent; the data from a single experiment provide all-sky images at wavelengths never before explored, covering more than three decades in angular scale with a signal dynamic range exceeding a factor of a million. These data open new avenues of research in fields ranging from Galactic astrophysics to cosmology. Our present Universe has shown herself to be both simple and elegant, and although her origins remain enshrouded in mystery, it appears that her past may have been more complex. While the Planck data have begun to inform us about the nature of cosmo-genesis,

Detecting Modified Gravity in the Stars – Jeremy Sakstein Mon. April 29th, 2013
10:30 am-11:30 am

Screened scalar-tensor gravity such as chameleon and symmetron theories allow order one deviations from General Relativity on large scales whilst satisfying all local solar-system constraints. A lot of recent work has therefore focused on searching for observational signatures of these models and constraining them. If these models are to be viable then our own solar system is necessarily screened, however, this may not be the case for stars in dwarf galaxies, which can exhibit novel and unique phenomena. These new effects can be exploited to produce constraints that are far more competitive than laboratory and cosmological tests and in this talk,

Senior Project Symposium Sat. April 20th, 2013
11:30 am-12:30 pm
In search for hints of resonance in the CMB power spectrum – Daan Meerburg Tue. April 16th, 2013
11:30 am-12:30 pm

We investigate possible resonance effects in the primordial power spectrum using the latest CMB data. These effects are predicted by a wide variety of models and come in two flavors, one where the oscillations are log spaced and one where the oscillations are linearly spaced. We treat the oscillations as perturbations on top of the scale invariant power spectrum. This allows us to significantly improve the search for resonance because it allows us to precompute the transfer functions. We show that the largest error from this simplification comes from the variance in the measurement to the distance of last scattering.

Black Hole Space-Times from S Matrices – Ira Rothstein Tue. April 9th, 2013
11:30 am-12:30 pm

In this talk I will show how to generate classical space-times directly from S matrices. The method makes no use of Einsteins’ equations nor, for that matter, any space-time action at all. This approach also allows us to make direct contact between the classical solutions of Yang-Mills theory and those of gravity through the squaring relation between the Yang-Mills and gravitational tree level scattering amplitudes. In this way one may construct classical space-times directly from Yang-Mills theory. – 

Testing gravity with pulsars, black holes and the microwave background – Lam Hui Tue. April 2nd, 2013
11:30 am-12:30 pm

We will discuss 3 topics: 1. a way to detect gravitational waves using binaries; 2. a way to test general relativity using black holes; 3. a way to connect superhorizon fluctuations with the observed statistical asymmetry of the universe.

Neutrinoless double beta decay results from EXO-200 – Carter Hall Tue. March 26th, 2013
11:30 am-12:30 pm

Neutrinoless double beta decay has never been definitively observed, although for the last ten years one group has claimed to see a 6-sigma positive effect in 76Ge. Recently the EXO-200 experiment produced the first independent check on this claim using 136Xe. This talk will report on the double beta decay results from EXO-200 and other experiments, along with prospects for future progress in this field.

CMB Non-Gaussianity from Recombination and Fingerprints of Dark Matter – Cora Dvorkin Tue. February 26th, 2013
11:30 am-12:30 pm

In this talk, I show that dark matter annihilation around the time of recombination can lead to growing ionization perturbations, that track the linear collapse of matter overdensities. This amplifies small scale cosmological perturbations to the free electron density by a significant amount compared to the usual acoustic oscillations. Electron density perturbations distort the CMB, inducing secondary non-gaussianity, offering a means of detection by Planck and other experiments. I will present a novel analytic calculation of CMB non-gaussianity from recombination, providing a clear identification of the relevant physical processes. I will show that, even though electron perturbations can be markedly boosted compared with the standard model prediction,

Odd tensor modes from particle production during inflation – Lorenzo Sorbo Tue. December 4th, 2012
11:30 am-12:30 pm

Several mechanisms can lead to production of particles during primordial inflation. I will review how such a phenomenon occurs and I will discuss how it can lead to the generation of tensor modes with unusual properties that might be detected in the not-so-far future. The gravitational waves produced this way can have a larger amplitude than in the standard scenarios, can violate parity, and their spectrum can display a feature that can be directly detected within the decade by second-generation gravitational interferometers such as advanced LIGO.

Advances in Solving the Two-Body Problem in General Relativity: Implications for the Search of Gravitational Waves – Alessandra Buonanno Tue. November 20th, 2012
11:30 am-12:30 pm

Compact binary systems composed of black holes and neutron stars are among the most promising sources for ground-based gravitational-wave detectors, such as the Laser Interferometer Gravitational Wave Observatory (LIGO) and its international partners. A detailed and accurate understanding of the shape of the gravitational waves is crucial not only for the initial detection of such sources, but also for maximizing the information that can be obtained from the gravitational-wave signals once they are observed. In this talk I will review progresses at the interface between analytical and numerical relativity. These advances have deepened our understanding of the two-body problem in general relativity,

Effective Field Theory for Fluids – Rachel Rosen Tue. November 13th, 2012
11:30 am-12:30 pm

In this talk I will present the low-energy effective field theory that describes the infrared dynamics of non-dissipative fluids. In particular, I will use the techniques of non-linear realizations developed by Callan, Coleman, Wess and Zumino, and Volkov to construct the effective theory based on the symmetry-breaking pattern of the fluid. I will discuss how this formalism can be used to incorporate quantum anomalies into the effective field theory.

Recent Results from CDMS II and The SuperCDMS Dark-matter Program – Raymond Bunker Tue. November 6th, 2012
11:30 am-12:30 pm

The Cryogenic Dark Matter Search experiment (CDMS II) was designed to directly detect dark matter by simultaneously measuring phonon and ionization signals caused by particle interactions in semiconductor targets, allowing event-by-event discrimination of signal from background via the relative sizes of the two signals. I’ll briefly review the CDMS II experiment and then focus on recent results related to the current low-mass WIMP controversy, including data from the CoGeNT, CRESST II, and DAMA/LIBRA experiments that hint at a low-mass WIMP signal and the (similarly sensitive) low-threshold and annual-modulation analyses performed by the CDMS II collaboration. I’ll also comment on the Collar and Fields likelihood analysis of the CDMS II low-energy data.

Kicking Chameleons: Early Universe Challenges for Chameleon Gravity – Adrienne Erickcek Tue. October 9th, 2012
11:30 am-12:30 pm

Chameleon gravity is a scalar-tensor theory that mimics general relativity in the Solar System. The scalar degree of freedom is hidden in high-density environments because the effective mass of the chameleon scalar depends on the trace of the stress-energy tensor. In the early Universe, when the trace of the stress-energy tensor is nearly zero, the chameleon is very light and Hubble friction prevents it from reaching its potential minimum. Whenever a particle species becomes non-relativistic, however, the trace of the stress energy tensor is temporarily nonzero, and the chameleon begins to roll. I will show that these “kicks” to the chameleon field have catastrophic consequences for chameleon gravity.

A new window on primordial non-Gaussianity – Enrico Pajer Tue. October 2nd, 2012
11:30 am-12:30 pm

We know very little about primordial curvature perturbations on scales smaller than about a Mpc. I review how mu-type distortion of the Cosmic Microwave Background spectrum provides the unique opportunity to probe these scales over the unexplored range from 50 to $104 Mpc-1$. This is a very clean probe, in that it relies only on well-understood linear evolution. While mu-distortion by itself can constrain the amount of power on small scales, correlations between mu-distortion and temperature anisotropies can be used to test Gaussianity. In particular the muT cross correlation is proportional to the very squeezed limit of the primordial bispectrum and hence measures $f_NL$ local,

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) – a new tool to probe the dark energy driven expansion history of the universe from z=1-3 – Matt Dobbs Tue. September 25th, 2012
11:30 am-12:30 pm

The most surprising discovery in cosmology since Edwin Hubble observed the expansion of the Universe isthat the rate of this expansion is accelerating. This either signals that a mysterious Dark Energy dominatesthe energy density of the Universe, or that our understanding of gravity on large scales is incorrect. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) will produce the largest volume astronomical survey to date, potentially unlocking the mysteries the dark-energy driven expansion history of the Universe. The CHIME telescope forms an image of the entire over-head sky each night by digitally processing the information received on a compact array of 2500 radio receivers.

Non-Gaussianity from general inflationary states – Nishant Agarwal Tue. September 18th, 2012
11:30 am-12:30 pm

I will describe the effects of non-trivial initial quantum states for inflationary fluctuations within the context of the effective field theory for inflation. We find that besides giving rise to large non-Gaussianities from inflation, general initial states can also have interesting implications for the consistency relation of the bispectrum. In addition, they leave a distinct observable signature on the scale-dependence of the bias of dark matter halos. I will also discuss constraints on the initial state from current large scale structure data, including luminous red galaxies and quasars in the Sloan Digital Sky Survey sample.

Boosting the Universe: Observational consequences of our motion – Amanda Yoho Tue. September 11th, 2012
11:30 am-12:30 pm

The Cosmic Microwave Background (CMB), photons from the earliest epoch that are able to free stream towards us, provides a unique opportunity to learn about many properties of the universe we live in. Already, the temperature fluctuations of the CMB have been studied by the Wilkinson Anisotropy Probe (WMAP) and have allowed many cosmological parameters to be pinned down to within a percent error. However, there are many more mysteries to be uncovered by precise measurements of the CMB polarization of these photons and weak lensing fields. Only with a robust understanding of the possible contaminants and astrophysical effects that can deform the measured fields will we be able to accurately characterize which models are favored over others.

The interplay between high and low redshift universe – Azadeh Moradinezhad Dizgah Tue. September 4th, 2012
11:30 am-12:30 pm

Download the slides

Supersymmetry, Naturalness, and the LHC: Where Do We Stand? – Matthew Reece Tue. May 1st, 2012
11:30 am-12:30 pm

The LHC has accumulated a large luminosity and has already begun ruling out a wide range of theoretical scenarios. I will discuss the theoretical implications of current LHC searches for supersymmetry and the first tentative Higgs measurements. In particular, I will assess the current status of SUSY naturalness, and explain some ways in which searches for the scalar top quark might help to further constrain the parameter space.

Gravitational Wave Detection with Pulsars: the NANOGrav collaboration – Dan Stinebring Tue. April 24th, 2012
11:30 am-12:30 pm

The effort to detect long-wavelength gravitational waves with a pulsar timing array (PTA) is progressing well, with three major international groups intensifying their efforts and increasingly sharing data and techniques. *Your* PTA, the North American Nanohertz Observatory for Gravitational waves (NANOGrav) is making excellent progress. I will report on our recent results and also comment on my group’s specialty, the effort to remove time variable propagation delays through the ionized interstellar medium.

Hunting for de Sitter vacua in the String Landscape – Gary Shiu Tue. April 17th, 2012
11:30 am-12:30 pm

Results from observational cosmology suggest that our universe is currently accelerating. The simplest explanation is that we are living in a universe with a positive cosmological constant. In this talk, I will describe some recent attempts in constructing such solutions in string theory and discuss the difficulties one encounters in finding metastable de Sitter vacua. Thus, the requirement of positive cosmological constant and stability imposes strong constraints on the string theory landscape.

Bosonic and Fermionic Non-thermal Dark Matter Isocurvature Perturbations and Non-Gaussianities – Daniel Chung Tue. April 10th, 2012
11:30 am-12:30 pm

Dark matter candidates in a broad class of non-thermal models produce primordial isocurvature perturbations and non-Gaussianities. We discuss the model dependence of such scenarios. In particular, fermionic superheavy dark matter requires non-gravitational interactions to be observationally interesting. We also present a general mathematical result regarding the cross correlation between the primordial isocurvature perturbations and curvature perturbations. This last result is of general interest for isocurvature phenomenology. Download the slides

Ghost-free multi-metric interactions Tue. April 3rd, 2012
11:30 am-12:30 pm

The idea that the graviton may be massive has seen a resurgence of interest due to recent progress which has overcome its traditional problems. I will review this recent progress, and show how the theory can be extended to write consistent interactions coupling together multiple massive spin-2 fields. Download the slides

Chromo-Natural Inflation – Peter Adshead Tue. March 27th, 2012
11:30 am-12:30 pm

I will describe a new model for inflation – Chromo-Natural Inflation – consisting of an axionic scalar field coupled to a set of three non-Abelian gauge fields. The model’s novel requirement is that the gauge fields begin inflation with a rotationally invariant vacuum expectation value (VEV) that is preserved through identification of SU(2) gauge invariance with rotations in three dimensions. The gauge VEV interacts with the background value of the axion, leading to an attractor solution that exhibits slow roll inflation even when the axion decay constant has a natural value (\less M_{\rm Pl}). Assuming a sinusoidal potential for the axion,

Testing the concordance cosmology with weak gravitational lensing – Ali Vanderveld Tue. March 20th, 2012
11:30 am-12:30 pm

Weak gravitational lensing, whereby the images of background galaxies are distorted by foreground matter, can be a powerful cosmological probe if systematics are sufficiently controlled. In particular, I will show how we may use weak lensing to robustly test the standard cosmological constant-dominated “concordance model” of cosmology by using in-hand expansion history data to make predictions for future observations. I will then discuss one recent proposal for economically gathering the necessary data while minimizing systematics — the balloon-borne High Altitude Lensing Observatory (HALO). Download the slides

An estimator for statistical anisotropy from the CMB bispectrum – Ema Dimstrogiovanni Tue. February 28th, 2012
11:30 am-12:30 pm

Various data analysis of the Cosmic Microwave Background (CMB) radiation present anomalous features that can be interpreted as indications of statistical isotropy breaking. Some models of inflation involving vector fields predict statistical anisotropy in the correlation functions of primordial curvature perturbations. We employ a simplified vector field model and parametrize the bispectrum of curvature fluctuations in such a way that all the information about statistical anisotropy is encoded in some coefficients lambda_{LM} (representing the ratio of the anisotropic to the isotropic bispectrum amplitudes). We compute an optimal estimator for these coefficients and their Fisher error. We predict a sensitivity for an experiment like Planck to the anisotropic to isotropic amplitudes of about 10% if fNL is around 30.

Local Primordial non-Gaussianity in Large-scale Structure – Marilena LoVerde Tue. February 21st, 2012
11:30 am-12:30 pm

Primordial non-Gaussianity is among the most promising of few observational tests of physics at the inflationary epoch. At present non-Gaussianity is best constrained by the cosmic microwave background, but in the near term large-scale structure data may be competitive so long as the effects of primordial non-Gaussianity can be modeled through the non-linear process of structure formation. I will discuss recent work modeling effects of a few types of primordial non-Gaussianity on the large-scale halo clustering and the halo mass function. More specifically, I will compare analytic and N-body results for two variants of the curvaton model of inflation: (i) a “tau_NL”

Inflation, or What? – William Kinney Tue. February 14th, 2012
11:30 am-12:30 pm

Cosmological inflation is the leading candidate theory for the physics of the early universe, and is in beautiful agreement with current cosmological data such as the WMAP Cosmic Microwave Background measurement. I consider alternatives to inflation with a critical eye, and present a simple argument showing that any model which matches the observed universe must have one of three properties: (1) accelerated expansion, (2) speed of sound faster than the speed of light, or (3) super-Planckian energy density. Download the slides

Quantum Kinetics and Thermalization of Hawking Radiation – Dmitry Podolsky Tue. February 7th, 2012
11:30 am-12:30 pm

Hawking’s discovery of black holes radiance along with Bekenstein’s conjecture of the generalized second law of thermodynamics inspired a conceptually pleasing connection between gravity, thermodynamics and quantum theory. However, the discovery that the spectrum of the radiation is in fact thermal, together with the no-hair theorem, has brought along with it some undesirable consequences, most notably the information loss paradox. There have been many proposals to the resolution of this paradox, with the most natural resolution being that during the time of collapse the radiation given off is not completely thermal and can carry small amounts of information with it.

Condensates and quasiparticles in inflationary cosmology – Daniel Boyanovsky Mon. February 6th, 2012
11:30 am-12:30 pm

Correlation functions during inflation feature infrared effects that could undermine a perturbative study. I will discuss self-consistent mechanisms of mass generation that regulates infrared physics, and introduce a method based on quantum optics to obtain the decay width of quantum states. Lack of energy conservation entails that EVERY particle acquires a width as a result of emission and absorption of superhorizon quanta thus becoming “quasiparticles”. BLACKBOARD TALK

Gravitational Waves from Cosmological Phase Transitions – Tom Giblin Tue. January 31st, 2012
11:30 am-12:30 pm

Cosmological phase transitions occurred. I will talk about recent advances in modeling possible phase transitions when these transitions are mediated by scalar fields. I will discuss first- and second-order transitions, at various scales, and show how we can compute the background of stochastic gravitational waves produced during (and after) these transitions.

Spatially Covariant Theories of a Transverse, Traceless Graviton – Godfrey Miller Tue. January 24th, 2012
11:30 am-12:30 pm

General relativity is a generally covariant, locally Lorentz covariant theory of two transverse, traceless graviton degrees of freedom. According to a theorem of Hojman, Kuchar, and Teitelboim, modifications of general relativity must either introduce new degrees of freedom or violate the principle of local Lorentz covariance. In this paper, we explore modifications of general relativity that retain the same graviton degrees of freedom, and therefore explicitly break Lorentz covariance. Motivated by cosmology, the modifications of interest maintain explicit spatial covariance. In spatially covariant theories of the graviton, the physical Hamiltonian density obeys an analogue of the renormalization group equation which encodes invariance under flow through the space of conformally equivalent spatial metrics.

Dark matter bounds from direct and indirect searches – Aravind Natarajan Tue. November 22nd, 2011
11:30 am-12:30 pm

I discuss ways of constraining dark matter properties using a combination of direct and indirect dark matter measurements. The DAMA, CoGeNT, and CRESST experiments have obtained tentative evidence for low mass WIMPs. I show that the CMB is a clean probe of low mass WIMPs, and the WMAP+SPT measurements place competitive bounds on light WIMPs. I discuss how these dark matter bounds may be further improved by including other data sets, such as counts of galaxy clusters.

Light does not always travel on the light cone – Yi-Zen Chu Tue. November 15th, 2011
11:30 am-12:30 pm

Massless particles such as photons and gravitons do not travel solely on the null cone in a generic curved spacetime. They propagate at all speeds equal to and less than c. This fact does not appear to be well appreciated in cosmology, and its consequences deserve to be worked out to ensure we are interpreting observations correctly. A rather dramatic (and hypothetical) example would be the following: suppose a significant fraction of photons from a distant supernova travels slower than c, then we may be mislead into thinking the SN is dimmer than it actually is, because some of the light has not arrived yet.

Holographic Quantum Quench – Sumit Das Fri. November 11th, 2011
11:30 am-12:30 pm

The holographic correspondence between non-gravitational field theories and gravitational theories in one higher dimension can be used to study non-equilibrium behavior of strongly coupled quantum field theories. One such phenomenon is that of quantum quench, where a coupling of the field theory is time dependent and typically asymptotes to constants at early and late times. In the gravity dual this can describe, under suitable circumstances, either black hole formation, or passage through a spacelilke region of high curvature similar to a cosmological singularity. On one hand this has taught us about the meaning of cosmological singularities, while on the other hand this has thrown light on the process of thermalization in strongly coupled field theories.

A Paradise Island for Deformed Gravity – Florian Kuehnel Tue. November 8th, 2011
11:30 am-12:30 pm

I will discuss our recently-proposed model (hep-th/1106.3566) of deformations of general relativity that are consistent and potentially phenomenologically viable, since they respect cosmological backgrounds. These deformations have unique symmetries in accordance with unitarity requirements, and give rise to a curvature induced self-stabilizing mechanism. Furthermore, our findings include the possibility of consistent and potentially phenomenologically viable deformations of general relativity that are solely operative on curved spacetime geometries, reducing to Einstein’s theory on the Minkowski background. I will also comment on possible phenomenological implications.

Measuring the dark sector with clusters of galaxies – Douglas Clowe Tue. November 1st, 2011
11:30 am-12:30 pm

Since Zwicky (1933), we have known that clusters of galaxies have gravitational potentials which are too large to be explained by the amount of visible baryons under the assumption of a Newtonian gravitational force law. This has led to competing hypotheses that either the masses of clusters are dominated by a non-baryonic form of matter or that gravity departs from a 1/r^2 force law on cluster scales. By using merging clusters of galaxies, I will show that the different types of matter in the clusters can be spatially seperated and, by using gravitational lensing, I will prove, independent of any assumptions about the nature of the law of gravity,

Carving Out the Space of Conformal Field Theories – David Simmons-Duffin Fri. October 28th, 2011
11:30 am-12:30 pm

Conformal Field Theories (CFTs) are theories that are symmetric under changes of distance scale, like a fractal or a Russian doll. They are basic building blocks of more general Quantum Field Theories, which can describe how nature works at its most fundamental level. Despite their importance, the range of possible behavior in CFTs is poorly understood, and often the most interesting theories resist calculation with conventional perturbative methods. However, over the last few years, new techniques have emerged for mapping out the space of these important theories. I’ll explain how to use basic mathematical consistency conditions, techniques from optimization theory (a subfield of computer science),

Understanding Chameleon Scalar Fields via Electrostatic Analogy – Kate Jones-Smith Tue. October 18th, 2011
11:30 am-12:30 pm

The late-time accelerated expansion of the universe could be caused by a scalar field that is screened on small scales, as in chameleon or symmetron scenarios. We present an analogy between such scalar fields and electrostatics, which allows calculation of the chameleon field profile for general extended bodies. Interestingly, the field demonstrates a `lightning rod’ effect, where it becomes enhanced near the ends of a pointed or elongated object. Drawing from this correspondence, we show that non-spherical test bodies immersed in a background field will experience a net torque caused by the scalar field. This effect, with no counterpart in the gravitational case,

How Asymmetric Dark Matter May Alter the Conditions of Stardom – Andrew Zentner Tue. September 27th, 2011
11:30 am-12:30 pm

Numerous recent experimental results have reinforced interest in a class of models dubbed “Asymmetric Dark Matter” (ADM), in which the relic dark matter density results from a particle-antiparticle asymmetry. Early models of this sort were invoked to explain the fact that the cosmic baryon and dark matter densities are of the same order, yet in the standard cosmology, they are produced by distinct physical processes. In such models, the relic dark matter density results from an asymmetry (perhaps dark matter carries B-L charge), so there are no contemporary cosmic dark matter annihilations and no opportunity for indirect detection. Otherwise, these scenarios give essentially the same cosmological predictions as the standard weakly-interacting massive particle/cold dark matter paradigm,

How the genome folds – Erez Lieberman Aiden Fri. September 23rd, 2011
11:30 am-12:30 pm

I describe Hi-C, a novel technology for probing the three-dimensional architecture of whole genomes by coupling proximity-based ligation with massively parallel sequencing. Working with collaborators at the Broad Institute and UMass Medical School, we used Hi-C to construct spatial proximity maps of the human genome at a resolution of 1Mb. These maps confirm the presence of chromosome territories and the spatial proximity of small, gene-rich chromosomes. We identified an additional level of genome organization that is characterized by the spatial segregation of open and closed chromatin to form two genome-wide compartments. At the megabase scale, the chromatin conformation is consistent with a fractal globule,

Lumps and bumps in the early universe: (p)reheating and oscillons after inflation – Mustafa Amin Tue. September 20th, 2011
11:30 am-12:30 pm

Our understanding of the universe between the end of inflation and production of light elements is incomplete. How did inflation end? What did the universe look like at the end of inflation? In this talk, I will discuss the different scenarios of (p)reheating: particle production at the end of inflation. I will then concentrate on a particular scenario: the fragmentation of the inflaton into localized, long-lived excitations of the inflaton field (oscillons), which end up dominating the energy density of the universe if couplings to other fields are weak. Oscillons are produced in a large class of inflationary models which are theoretically well motivated and observationally consistent with the cosmic microwave background anisotropies.

Massive gravitons and enhanced gravitational lensing – Mark Wyman Tue. April 26th, 2011
11:30 am-12:30 pm

The mystery of dark energy suggests that there is new gravitational physics at low energies and on long length scales. On the other hand, low mass degrees of freedom in gravity are strictly limited by observations within the solar system. A compelling way to resolve this apparent contradiction is to add a galilean-invariant scalar field to gravity. Called galileons, these scalars have strong self interactions near overdensities, like the solar system, that suppress their effects on the motion of massive particles. These non-linearities are weak on cosmological scales, permitting new physics to operate. Extending galilean invariance to the coupling of galileons to stress-energy —

Learning about Aspects of Clusters and Cosmology from Weak and Strong Gravitational Lensing Approaches – Mandeep Gill Tue. April 12th, 2011
11:30 am-12:30 pm

I will cover several aspects of current astrophysics that can be probed by various regimes of lensing in simulations and data –from galaxy cluster substructure to what we can learn about cosmology from cluster weak lensing ensembles. Further, a new approach to extracting information from strongly lensed arc images that I have been involved with in recent times, and which is model-independent and has the potential to revolutionize approaches to strong lensing analyses and is very complementary to weak lensing analyses will be introduced. I will further briefly discuss initial lensing results from already-taken data of 6 clusters from the Large Binocular Telescope in Arizona,

Thick-wall tunneling in a piecewise linear and quadratic potential – Pascal Vaudrevange Tue. April 12th, 2011
11:30 am-12:30 pm

After reviewing the basics of Coleman deLuccia tunneling, especially in the thin-wall limit, I discuss an (almost) exact tunneling solution in a piecewise linear and quadratic potential. A comparison with the exact solution for a piecewise linear potential demonstrates the dependence of the tunneling rate on the exact shape of the potential. Finally, I will mention applications when determining initial conditions for inflation in the landscape. Based on arXiv:1102.4742 [hep-th].

Gravitational wave astronomy in the next decade – Xavier Siemens Tue. April 5th, 2011
11:30 am-12:30 pm

In the next decade two types of gravitational wave experiments are expected to result in the direct detection of gravitational waves: Advanced ground-based interferometric detectors and pulsar timing experiments. In my talk I will describe both types of experiments and their sensitivities to various types of gravitational wave sources. I will also discuss some of the impacts of these experiments on astronomy and cosmology.

Testing Dark Energy with Massive Galaxy Clusters – Michael Mortonson Tue. March 29th, 2011
11:30 am-12:30 pm

Existing observations of the cosmic expansion history place strong restrictions on the rate of large scale structure growth predicted by various dark energy models. In the simplest Lambda CDM scenario, current observations enable percent-level predictions of growth, which can be interpreted in terms of the expected abundance of massive galaxy clusters at high redshift. I will show that these predictions from current data set a firm upper limit on the cluster abundance in the more general class of quintessence models where dark energy is a canonical, minimally-coupled scalar field. While the most massive clusters known today appear to lie just below this limit,

New observational power from halo bias – Sarah Shandera Tue. March 22nd, 2011
11:30 am-12:30 pm

Non-Gaussianity of the local type will be particularly well constrained by large scale structure through measurements of the power spectra of collapsed objects. Motivated by properties of early universe scenarios that produce observationally large local non-Gaussianity, we suggest a generalized local ansatz and perform N-body simulations to determine the signatures in the bias of dark matter halos. The ansatz introduces two bispectral indices that characterize how the local non-Gaussianity changes with scale and these generate two new signals in the bias. While analytic predictions agree qualitatively with the simulations, we find numerically a stronger observational signal than expected, which suggests that a better analytic understanding is needed to fully explain the consequences of primordial non-Gaussianity.

Constraining the cosmic growth history with large scale structure – Rachel Bean Tue. March 15th, 2011
11:30 am-12:30 pm

We consider how upcoming, prospective large scale structure surveys, measuring galaxy weak lensing, position and peculiar velocity correlations, in tandem with the CMB temperature anisotropies, will constrain dark energy when both the expansion history and growth of structure can be modified, as might arise if cosmic acceleration is due to modifications to GR. We consider an equation of state figure of merit parameter, and analogous figure of merit parameters for modified gravity, to quantify the relative constraints from CMB, galaxy position, lensing, and peculiar velocity observations and their cross correlations, independently and in tandem.

What to do with 350,000 astronomers – Chris Lintott Fri. February 18th, 2011
11:30 am-12:30 pm

Since its launch in 2007, the Galaxy Zoo project has involved hundreds of thousands of volunteers in the morphological classification of galaxies. Project PI Chris Lintott will review the results – which include a new understanding of the importance of red spirals – and their implications for our understanding of galaxy formation. The project has now expanded to include tasks ranging from discovering planets through to lunar classification, and the talk will also discuss the potential of this ‘citizen science’ method to help scientists cope with massive modern data sets.

Astrophysics with Gravitational-Wave Detectors – Vuk Mandic Tue. February 8th, 2011
11:30 am-12:30 pm

Gravitational waves are predicted by the general theory of relativity to be produced by accelerating mass systems with quadrupole moment. The amplitude of gravitational waves is expected to be very small, so the best chance of their direct detection lies with some of the most energetic events in the universe, such as mergers of two neutron stars or black holes, Supernova explosions, or the Big-Bang itself. I will review the status of current gravitational-wave detectors, such as the Laser Interferometer Gravitational-wave Observatory (LIGO), as well as some of the most recent results obtained using LIGO data. I will also discuss plans and expectations for the future generations of gravitational-wave detectors.

New and Old Massive Gravity – Claudia de Rham Tue. February 1st, 2011
11:30 am-12:30 pm

TBA

A new method for cosmological parameter estimation from Supernovae Type Ia data – Marisa March Tue. January 18th, 2011
11:30 am-12:30 pm

We present a new methodology to extract constraints on cosmological parameters from SNIa data obtained with the SALT lightcurve fitter. The power of our Bayesian method lies in its full exploitation of relevant prior information, which is ignored by the usual chisquare approach. Using realistic simulated data sets we demonstrate that our method outperforms the usual chisquare approach 2/3 of the times. A further benefit of our methodology is its ability to produce a posterior probability distribution for the intrinsic dispersion of SNe. This feature can also be used to detect hidden systematics in the data.

K-essence Interactions with Neutrinos: Flavor Oscillations without Mass – Christopher Gauthier Tue. December 7th, 2010
11:30 am-12:30 pm

In this talk we discuss a novel means of coupling neutrinos to a Lorentz violating background k-essence field. K-essence is a model of dark energy, which uses a non-canonical scalar field to drive the late time accelerated expansion of the universe. We propose that neutrinos couple to the k-essence induced metric rather than the space-time metric. The immediate effect that this has will be to modify the energy-momentum relation of the neutrino. This implies that the neutrino velocity will in general be different from the speed of light, even if the neutrino is massless. Later we will see that k-essence can also induce neutrino oscillations even without a neutrino mass term.

Light from Cosmic Strings – Tanmay Vachaspati Tue. November 16th, 2010
11:30 am-12:30 pm

TBA

Testing the No-Hair Theorem with Astrophysical Black Holes – Dmitrios Psaltis Tue. November 2nd, 2010
11:30 am-12:30 pm

The Kerr spacetime of spinning black holes is one of the most intriguing predictions of Einstein’s theory of general relativity. The special role this spacetime plays in the theory of gravity is encapsulated in the no-hair theorem, which states that the Kerr metric is the only realistic black-hole solution of the vacuum field equations. Recent and anticipated advances in the observations of black holes throughout the electromagnetic spectrum have secured our understanding of their basic properties while opening up new opportunities for devising tests of the Kerr metric. In this talk, I will show how imaging and spectroscopic observations of accreting black-holes with current and future instruments can lead to the first direct test of the no-hair theorem with an astrophysical object.

Cosmological Constraints from Peculiar Velocities – Arthur Kosowski Fri. October 29th, 2010
11:30 am-12:30 pm

Peculiar velocities of galaxies and clusters are induced during the formation of structure in the universe via gravitational forces. As such, they provide a potentially powerful route to constraining both the growth of structure and the expansion history of the universe. Traditional methods of velocity determination have not yet been able to measure velocities at cosmological distances with sufficient accuracy to allow cosmological constraints. I will discuss two possible methods of measuring peculiar velocities: directly via the kinematic Sunyaev-Zeldovich effect for galaxy clusters, and using distance measurements of type-Ia supernovae in future large surveys. I will discuss measurement prospects, and show that upcoming probes of mean pairwise velocity will have the potential to plac significant constraints on both dark energy and modifications of gravity while limiting systematic errors

IR issues in Inflation – Richard Holman Fri. October 15th, 2010
11:30 am-12:30 pm

I review some problems involving IR divergences in de Sitter space that give rise to behavior such as secular growth of fluctuations and discuss the use of the Dynamical Renormalization Group as a tool to resum and reinterpret these divergences. Time permitting, I’ll also discuss some more recent work on the breakdown of the semiclassical approximation in de Sitter space.

The Angular Distribution of the Highest-Energy Cosmic Rays – Andrew Jaffe Tue. October 12th, 2010
11:30 am-12:30 pm

TBA

Bulk viscosity and the damping of neutron star oscillations – Mark Alford Fri. October 8th, 2010
11:30 am-12:30 pm

How do we learn about the phases of matter beyond nuclear density? They are to be found only in the interior of neutron stars, which are inaccessible and hard to observe. One approach is through the oscillations of neutron stars, which depend on the viscosity of their interior. If the viscosity is low enough then “r-mode” oscillations arise spontaneously and cause the star to spin down. Finding fast-spinning stars therefore puts limits on the viscosity viscosity and hence on the possible phases present in the interior of the star. This talk discusses non-linear effects which arise for large amplitude “suprathermal”

CMB in a Box – Raul Abramo Tue. September 28th, 2010
11:30 am-12:30 pm

First, I will show that the line-of-sight solution to cosmic microwave anisotropies in Fourier space, even though formally defined for arbitrarily large wavelengths, leads to position-space solutions which only depend on the sources of anisotropies inside the past light-cone of the observer. This happens order by order in a series expansion in powers of the visibility function. Second, I will show that the Fourier-Bessel expansion of the physical fields (including the temperature and polarization momenta) is superior to the usual Fourier basis as a framework to compute the anisotropies. In that expansion, for each multipole $l$ there is a discrete tower of momenta $k_{i,l}$ (not a continuum) which can affect physical observables,

Does Quantum Mechanics Imply Gravity? – Harsh Mathur Tue. September 21st, 2010
11:30 am-12:30 pm

TBA

Galileon Inflation and Non-Gaussianities – Andrew Tolley Tue. September 7th, 2010
11:30 am-12:30 pm

I will discuss a new class of inflationary models based upon the idea of Galileon fields, scalar fields that exhibit non-linearly realized symmetries. These models predict distinctive non-Gaussian features in the primordial power spectrum, and I will discuss how they relate with, and can be distinguished from, canonical inflation, k-inflation, ghost inflation, and DBI-inflationary models.

Michelson Lectures — High-Energy Physics with Low-Energy Symmetry Studies – David Hanneke Fri. May 14th, 2010
11:30 am-12:30 pm

Discrete symmetries — charge conjugation (C), parity inversion (P), time reversal (T), and their combinations — provide insight into the structure of our physical theories. Many extensions to the Standard Model predict symmetry violations beyond those already known. From the first evidence of P-violation in the 1950s using cold atoms, low-energy, high-precision experiments have quantified existing violations and constrained further ones. In this lecture, I will describe several searches for discrete symmetry violations with low-energy experiments. T-violation, closely related to matter/antimatter asymmetry through the CPT theorem, is tightly constrained by searches for intrinsic electric dipole moments. CPT-violation — the only combination of these symmetries obeyed by the entire Standard Model —

Michelson Lectures — Cavity Control in a Single-Electron Quantum Cyclotron: An Improved Measurement of the Electron Magnetic Moment – David Hanneke Thu. May 13th, 2010
11:30 am-12:30 pm

Measurements of the electron magnetic moment (the “g-value”) probe the electron’s interaction with the fluctuating vacuum. With a quantum electrodynamics calculation, they provide the most accurate determination of the fine structure constant. Comparisons with independent determinations of the fine structure constant are the most precise tests of quantum electrodynamics and probe extensions to the Standard Model of particle physics. I will present two new measurements of the electron magnetic moment. The second, at a relative uncertainty of 0.28 parts-per-trillion, yields a value of the fine structure constant with a relative accuracy of 0.37 parts-per-billion, over 10-times smaller uncertainty than the next-best methods.

Michelson Lectures — Optical Atomic Clocks – David Hanneke Tue. May 11th, 2010
11:30 am-12:30 pm

The most precise measurement techniques involve time, frequency, or a frequency ratio. For example, for centuries, accurate navigation has relied on precise timekeeping — a trend that continues with today’s global positioning system. After briefly reviewing the current microwave frequency standards based on the hyperfine structure of cesium, I will describe work towards atomic clocks working at optical frequencies. Among these are standards based on trapped ions or on neutral atoms trapped in an optical lattice. A frequency comb allows the comparison of different optical frequencies and the linking of optical frequencies to more-easily-counted microwave ones. Though still in the basic research stage,

Michelson Lectures — Entangled Mechanical Oscillators and a Programmable Quantum Computer: Adventures in Coupling Two-Level Systems to Quantum Harmonic Oscillators – David Hanneke Mon. May 10th, 2010
11:30 am-12:30 pm

The two-level system and the harmonic oscillator are among the simplest analyzed with quantum mechanics, yet they display a rich set of behaviors. Quantum information science is based on manipulating the states of two-level systems, called quantum bits or qubits. Coupling two-level systems to harmonic oscillators allows the generation of interesting motional states. When isolated from the environment, trapped atomic ions can take on both of these behaviors. The two-level system is formed from a pair of internal states, which lasers efficiently prepare, manipulate, and read-out. The ions’ motion in the trap is well described as a harmonic oscillator and can be cooled to the quantum ground state.

Cosmological Bubbles and Solitons: A Classic(al) Effect – Tom Giblin Tue. April 27th, 2010
11:30 am-12:30 pm

Cosmological bubble collisions arising from first order phase transitions are a generic consequence of the Eternal Inflation scenario. I will present our computational strategy for generating and evolving these bubbles in 3+1 dimensions and in a self-consistently expanding background. I will show the existence of classical field transitions–the classical nucleation of bubbles during collisions–which can dramatically alter the canonical description of eternal inflation.

CP Violation in Bs->J/psi phi: Evidence for New Physics? – Karen Gibson Tue. April 13th, 2010
11:30 am-12:30 pm

CP violation in the Bs->J/psi phi system has been one of the most discussed topics in particle physics in the past two years, in large part due to anomalously high, although statistically limited, measurements of the CP violating phase made by the Tevatron experiments. The measurement of this CP phase has been a highlight of the late Run II Tevatron physics effort and it’s precise determination is the flagship analysis of the LHCb program. I will present the physics interest in CP violation in the Bs system, give an overview of the past and present results from the Tevatron experiments,

Quantum Effects in Gravitational Collapse of a Reisner-Nordström Domain wall Tue. April 6th, 2010
11:30 am-12:30 pm

We will investigate the formation of RN black holes by studying the collapse of a charged spherically symmetric domain wall. Utilizing the Functional Schrödinger formalism, we will also investigate time-dependent thermodynamic properties of the collapse and compare with the well known theoretical results.

String theory cosmic strings – Dimitri P. Skliros Tue. March 30th, 2010
11:30 am-12:30 pm

I will discuss the first construction of coherent states in the covariant formalism for both open and closed strings with applications to cosmic strings in mind. Furthermore, I provide an explicit map that relates three different descriptions of cosmic strings: classical strings, lightcone gauge quantum states and covariant vertex operators. I will then go on to discuss applications and future directions: string amplitude computations with such vertices and in particular decays of (the phenomenologically promising) cosmic strings with non-degenerate cusps in a framework that naturally incorporates the effects of gravitational backreaction. Partly based on: http://arxiv.org/abs/0911.5354

Tunneling in Flux Compactifications – Jose Blanco-Pillado Tue. March 23rd, 2010
11:30 am-12:30 pm

We identify instantons representing several different transitions in a field theory toy model for string theory flux compactifications and described the observational signatures of such processes.

Primordial magnetic fields: evolution and observable signatures – Tina Kahniashvili Tue. March 16th, 2010
11:30 am-12:30 pm

I will discuss the evolution of the primordial magnetic field accounting for MHD instabilities in the early Universe. I will address different cosmological signatures of the primordial magnetic fields and will discuss the observational tests to limit the amplitude and correlation length of the magnetic fields, as well as their detection prospects.

ArDM Experiment – Carmen Carmona Tue. March 2nd, 2010
11:30 am-12:30 pm

The Argon Dark Matter (ArDM) project aims at operating a large noble liquid detector to search for direct evidence of Weakly Interacting Massive Particles (WIMP) as Dark Matter in the universe. It consists on a one-ton liquid argon detector able to read independently ionization charge and scintillation light. I will describe the experimental concept and the physics performance of the ArDM experiment, which is presently under construction and commissioning on surface at CERN.

A Theory Program to Exploit Weak Gravitational Lensing to Constrain Dark Energy – Andrew Zentner Fri. February 26th, 2010
11:30 am-12:30 pm

Weak gravitational lensing is one of the most promising techniques to constrain the dark energy that drives the contemporary cosmic acceleration. I give an overview of the dark energy problem, focusing on the manner in which weak gravitational lensing can determine the nature of the dark energy. Bringing lensing constraints to fruition is challenging both observationally and theoretically. I will focus on the theoretical challenges. The most demanding of these is to make accurate predictions for the power spectrum of density fluctuations on nonlinear scales, including treatments of baryonic processes such as galaxy formation, that have been neglected in much of the literature.

Shedding light on the nature of dark matter with gamma-rays – Jennifer Siegal-Gaskins Tue. February 23rd, 2010
11:30 am-12:30 pm

Detection of gamma rays from the annihilation or decay of dark matter particles is a promising method for identifying dark matter, understanding its intrinsic properties, and mapping its distribution in the universe. I will review recent results from the Fermi Gamma-ray Space Telescope and other experiments and discuss the constraints these place on particle dark matter models. I will also present a novel approach to extracting a dark matter signal from Fermi gamma-ray observations using the energy-dependence of anisotropies in a sky map of the diffuse emission. The sensitivity of this technique and its prospects for robustly identifying a dark matter signal in Fermi data will be discussed.

Non-gaussianities and the Inflationary Initial State – Andrew Tolley Fri. February 19th, 2010
11:30 am-12:30 pm

The potential discovery of primordial non-gaussianities would revolutionize our understanding of early universe cosmology, giving a whole new perspective on the physics responsible for inflation. I will review the different possible physical mechanisms that can give rise to non-gaussianities, and discuss in detail those which are distinctive in telling us about the inflationary quantum state. In particular, I will show how consistency conditions coming from effective field theory can be used to constrain the level of non-gaussianity that we can hope to observe in future data.

Dark Matter via Many Copies of the Standard Model – Alex Vikman Tue. February 16th, 2010
11:30 am-12:30 pm

Recently it was realized that the strong coupling scale in gravity substantially depends on the number of different quantum fields present in nature. On the other hand, gravity theory with an electroweak strong coupling scale could be responsible for a solution of the hierarchy problem. Consequently it was suggested that possible existence of very many hidden fields could stabilize the mass of Higgs particle. In this talk I review a cosmological scenario based on the assumption that the Standard Model possesses a large number of copies. It is demonstrated that baryons in the hidden copies of the standard model can naturally account for the dark matter.

Hierarchy in the Phase Space and Dark Matter Astronomy – Niayesh Afshordi Fri. February 12th, 2010
11:30 am-12:30 pm

Understanding small scale structure in the dark matter distribution is important in interpreting many astrophysical observations, as well as dark matter (direct or indirect) detection searches. With this motivation, I introduce a theoretical framework for describing the rich hierarchy of the phase space of cold dark matter haloes, due to gravitationally bound sub-structures, as well as tidal debris and caustics. I then argue that if/when we detect dark matter particles, a new era of Dark Matter Astronomy will be just around the corner.

Shading Lambda – Claudia de Rahm Tue. February 2nd, 2010
11:30 am-12:30 pm

The idea of degravitation is to tackle the cosmological constant problem by modifying gravity at large distances such that a large cosmological constant does not backreact as much as anticipated from standard General Relativity. After reviewing the fundamental aspects of degravitation, I will present a new class of theories of massive gravity capable of exihibiting the degravitation behaviour. I will then comment on the stability of such models and show in the decoupling limit how theories of gravity with at least two additional helicity-0 excitations can provide a stable realization of degravitation.

Dark Matter Substructure in the Milky Way: Properties and Detection Prospects – Louie Strigari Tue. January 26th, 2010
11:30 am-12:30 pm

Cosmological observations have converged on a standard model of Lambda-Cold Dark Matter (LCDM), in which the Universe is dominated by yet unknown components of dark matter and dark energy. When confronted with observations of our own Milky Way, this theory of LCDM leads to the prediction of a significant population of bound, unseen dark matter substructures, ranging possibly from Earth mass scales up to observed dwarf galaxy mass scales. In this talk, I will discuss the theory of LCDM and substructure in the context of present and forthcoming deep galaxy surveys, and show how these observations may be used to provide detailed predictions for the abundance and mass spectrum of dark substructures.

On triviality of $\lambda\phi^{4}$ theory in $D=4$ – Dmitry Podolsky Tue. January 19th, 2010
11:30 am-12:30 pm

e introduce a new non-perturbative method suitable for analyzing scalar quantum field theories at strong coupling based on mapping between quantum field theories in $dS_{D}\times M_{N}$ spacetime and statistical field theories in Euclidean space $M_{N}$. Applying this method to $\lambda\phi^{4}$ theory in $dS_{D}\times E_{4}$ spacetime, we analyze behavior of the 4-dimensional $\lambda\phi^{4}$ theory in the regime $\lambda\sim{}1$ and give a new argument in favor of triviality of the theory.

Pulsar Kicks With Active and Sterile Neutrinos – Leonard Kisslinger Fri. December 4th, 2009
11:30 am-12:30 pm

In 2007 my coworkers and I completed the calculation of the velocity given to a neutron star in the period of 10-20 seconds after the gravitational collapse of a massive star by active neutrinos. This year an analysis of neutrino data has shown that there exist sterile neutrinos with large mixing angles. We have calculated the velocity that the emission of such sterile neutrinos in the 0-10 second period would give to the neutron star (the pulsar). We are applying this to calculate the velocity of the neutron star that might have been formed by SN 1987A. We are also engaged in calculating sterile neutrino prosesses during a supernova collapse to see if the stalled shock can be unstalled.

Nongaussian Fluctuations from Particle Production During Inflation – Neil Barnaby Tue. November 24th, 2009
11:30 am-12:30 pm

In a variety of inflation models, the motion of the inflaton may trigger the production of some iso-curvature particles during inflation, for example via parametric resonance or a phase transition. Inflationary particle production provides a new mechanism for generating cosmological perturbations (infra-red cascading) and can also slow the motion of the inflaton on a steep potential. Moreover, such models provide a novel example of non-decoupling of high scale physics during inflation. I will discuss the observational consequences of inflationary particle production, including the generation of features in the primordial power spectrum and large nongaussianities with a unique shape of bispectrum.

Gravitational Waves, Laser Interferometers and Multimessenger Astrophysics – Laura Cadonati Tue. November 10th, 2009
11:30 am-12:30 pm

The Laser Interferometer Gravitational-wave Observatory (LIGO) and its sister project Virgo are currently acquiring data, aiming at the first direct detection of gravitational waves. These elusive ripples in the fabric of space-time, carriers of information on the acceleration of large masses, are a key prediction of General Relativity; their detection will activate a fundamental, new probe into the universe. Sources of interest for LIGO/Virgo include the coalescence of compact binary systems, core-collapse supernovae and the stochastic background from the early universe, as well as multi-messenger coincident signatures with electromagnetic or neutrino counterparts. In this talk, I will present the status of ground-based gravitational wave detectors and review the most significant observational results obtained so far.

Three thoughts about black holes and cosmology – Latham Boyle Tue. November 3rd, 2009
11:30 am-12:30 pm

I will present three ideas about black holes and cosmology. First, I will discuss a way of understanding the simple patterns which emerge from the notoriously thorny numerical simulations of binary black hole merger, and some of the directions where this understanding may lead. Second, I will suggest a sequence of practical bootstrap tests designed to give sharp observational confirmation of the essential idea underlying the inflationary paradigm: that the universe underwent a period of accelerated expansion followed by a long period of decelerated expansion. Third, I will investigate a way that one might try to detect the strong bending of light rays in the vicinity of a black hole.

Using anisotropy to identify a dark matter signal in diffuse gamma-ray emission with Fermi – Jennifer Siegal-Gaskins Tue. October 20th, 2009
11:30 am-12:30 pm

Dark matter annihilation in Galactic substructure will produce diffuse gamma-ray emission of remarkably constant intensity across the sky, making it difficult to disentangle this Galactic dark matter signal from the extragalactic gamma-ray background. Recent studies have considered the angular power spectrum of the diffuse emission from various extragalactic source classes and from Galactic dark matter. I’ll discuss these results and show how the energy dependence of anisotropies in the total measured diffuse emission could be used to confidently identify a signal from dark matter in Fermi data. Finally, I’ll present new results demonstrating that anisotropy analysis could significantly extend the sensitivity of current indirect dark matter searches.

Measuring small scale CMB temperature and polarization anisotropies with the Atacama Cosmology Telescope – Mike Niemack Fri. October 16th, 2009
11:30 am-12:30 pm

The Atacama Cosmology Telescope (ACT) is a six-meter telescope on the Atacama plateau, Chile that was built to characterize the cosmic microwave background (CMB) with arcminute resolution. Since 2008 ACT has been used to measure the temperature anisotropies in the CMB in three bands between 140 – 300 GHz with the largest arrays of transition-edge sensor (TES) bolometers ever fielded for CMB observations. Two of the primary science objectives for these measurements are: detecting galaxy clusters via the Sunyaev-Zel’dovich effect, which can be used to study the dark energy equation of state when combined with optical redshifts, and measuring the CMB power spectrum at high multipoles to improve constraints on cosmological parameters.

New Perspectives on Indirect, Astrophysical Dark Matter Limits – Andrew Zentner Fri. October 9th, 2009
11:30 am-12:30 pm

High-Energy neutrinos from the annihilations of dark matter captured within the Sun is thought to be a relatively clean, indirect probe of dark matter physics. In addition, this probe is sensitive to the dark matter-proton cross section so it can be used to cross-check direct searches, and does not rely on a large annihilation cross section in order to be observed in near-term experiments such as IceCube. I will consider a modification of the standard scenario. Dark matter that interacts strongly with itself as has been proposed in several contexts. I show that viable models of self-interacting dark matter can lead to large boosts in the expected neutrino flux from the Sun,

CMB Polarization Power Spectra from Two Years of BICEP Data – Cynthia Chiang Tue. September 22nd, 2009
11:30 am-12:30 pm

BICEP is a bolometric polarimeter designed to measure the inflationary B-mode polarization of the cosmic microwave background at degree angular scales. During three seasons of observing at the South Pole (2006–2008), BICEP mapped ~2% of the sky chosen to be uniquely clean of polarized foreground emission. I will discuss the initial maps and angular power spectra derived from a subset of the data acquired during the first two years, and I will describe in detail the analysis methods and studies of potential systematic errors. BICEP measures the E-mode power spectrum with high precision at 21 < ell < 335 and detects the acoustic peak expected at ell ~ 140 for the first time.

Cryogenic Dark Matter Search . Current Results and Future Background Discrimination – Cathy Bailey Tue. May 5th, 2009
11:30 am-12:30 pm

The Cryogenic Dark Matter Search (CDMS) is searching for Weakly Interacting Massive Particles (WIMPs) with cryogenic germanium particle detectors. These detectors discriminate between nuclear recoil candidate and electron recoil background events by collecting both phonon and ionization energy from recoils in the detector crystals. The CDMS II experiment has completed analysis of the first data run with 30 semiconductor detectors at the Soudan Underground Laboratory resulting in a world leading WIMP-nucleon spin-independent cross section limit for WIMP masses above 44 GeV/c2. As CDMS aims to achieve greater WIMP sensitivity, it is necessary to increase the detector mass and discrimination between signal and background events.

String shots from a spinning black hole – Ted Jacobson Fri. April 24th, 2009
11:30 am-12:30 pm

The dynamics of relativistic current carrying string loops moving axisymmetrically on the background of a Kerr black hole are characterized. In one interesting type of motion, a loop can be ejected along the axis, some internal elastic or rotational kinetic energy being converted into translational kinetic energy.

Fundamentals of the LHC – Johan Alwall Tue. April 14th, 2009
11:30 am-12:30 pm

In this introductory lecture I will present why we have built the LHC, and discuss the underlying physics of a hadron collider. This includes the fundamentals of QCD (the theory for the strong interaction), features such as jets and hadronization, and an introduction to the physics of the Standard Model, including Electroweak symmetry breaking. The lecture will be concluded with a discussion about the problems with the Standard Model.

The curvaton inflationary model, non-Gaussianity and isocurvature – Maria Beltran Tue. March 31st, 2009
11:30 am-12:30 pm

The inflationary paradigm has become one of the most compelling candidates to explain the observed cosmological phenomena. However, the data is still inconclusive about the particular details of the inflationary model. Apart from the basic, single field model, there exists a wide range of currently undistinguishable possibilities for the scalar field number, potential and couplings during the early universe. In this talk I will review one of these extensions of the basic inflationary model, the curvaton model, where at least two scalar fields are present during inflation. I will revisit the constraints on the parameters of the model in light of the results of recent non-Gaussianity analyses and bounds on the cold dark matter isocurvature contribution in the primordial anisotropies of the CMB.

Large-Scale Structure in Modified Gravity – Roman Scoccimarro Fri. March 27th, 2009
11:30 am-12:30 pm

Cosmic acceleration may be due to modifications of general relativity (GR) at large scales, rather than dark energy. We use analytic techniques and N-body simulations to find out what observational signatures to expect in brane-induced gravity, with focus on new nonlinear effects not present in GR.

Dark Stars – Katie Freese Tue. March 17th, 2009
11:30 am-12:30 pm

We have proposed that the first phase of stellar evolution in the history of the Universe may be Dark Stars (DS), powered by dark matter heating rather than by nuclear fusion. Weakly Interacting Massive Particles, which may be their own antipartners, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a Dark Star, powered by dark matter annihilation as long as there is dark matter fuel, with lifetimes from millions to billions of years. We find that the first stars are very bright (a million times solar) diffuse puffy objects during the DS phase,

Cascading Gravity and Degravitation – Claudia de Rham Tue. March 3rd, 2009
11:30 am-12:30 pm

Cascading gravity is an explicit realization of the idea of degravitation, where gravity behaves as a high-pass filter. This could explain why a large cosmological constant does not backreact as much as anticipated from standard General Relativity. The model relies on the presence of at least two infinite extra dimensions while our world is confined on a four-dimensional brane. Gravity is then four-dimensional at short distances and becomes weaker at larger distances.

Testing global isotropy and some interesting cosmological models with CMB – Amir Hajian Tue. February 24th, 2009
11:30 am-12:30 pm

Simplest models of the Universe predict global (statistical) isotropy on large scales in the observable Universe. However there are a number of interesting models that predict existence of preferred directions. In this talk I will present results of using CMB anisotropy maps to test the global isotropy of the Universe on its largest scales, and will show how that can help us constrain interesting models such as topology of the Universe and anisotropic cosmological models (e.g. Bianchi models). I will also discuss the intriguing lack of power on large angular scales in the observed CMB maps and implications that it may have for cosmology.

Hilltop Quintessence – Sourish Dutta Tue. February 17th, 2009
11:30 am-12:30 pm

We examine hilltop quintessence models, in which the scalar field is rolling near a local maximum in the potential, and w is close to -1. We first derive a general equation for the evolution of the scalar field in the limit where w is close to -1. We solve this equation for the case of hilltop quintessence to derive w as a function of the scale factor; these solutions depend on the curvature of the potential near its maximum. Our general result is in excellent agreement (delta w < 0.5%) with all of the particular cases examined. It works particularly well (delta w <

Can the WMAP Haze really be a signature of annihilating neutralino dark matter? – Daniel Cumberbatch Tue. February 3rd, 2009
11:30 am-12:30 pm

Observations by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite have identified an excess of microwave emission from the centre of the Milky Way. It has been suggested that this {\it WMAP haze} emission could potentially be synchrotron emission from relativistic electrons and positrons produced in the annihilations of one (or more) species of dark matter particles. In this paper we re-calculate the intensity and morphology of the WMAP haze using a multi-linear regression involving full-sky templates of the dominant forms of galactic foreground emission, using two different CMB sky signal estimators. The first estimator is a posterior mean CMB map,

Multi-brane Inflation in String Theory – Amjad Ashoorioon Tue. January 27th, 2009
11:30 am-12:30 pm

I will talk about two inflationary scenarios in which the cooperative behavior of multiple branes give rise to inflation. In the first one, which we call cascade inflation, assisted inflation is realized in heterotic M-theory and by non-perturbative interactions of N M5-branes. The features in the inflaton potential are generated whenever two M5-branes collide with the boundaries. The derived small-scale power suppression could serves as a possible explanation for the dearth of observed dwarf galaxies in the Milky Way halo. In the second one, the transverse dimension of coincident D3-branes, which are N-dimensional matrices, result in inflation. We discuss how various scenarios such as chaotic,

High temperature superfluidity in high energy heavy ion collisions at RHIC and forward physics with TOTEM at LHC – Tamas Csorgo Tue. January 13th, 2009
11:30 am-12:30 pm

Five important milestones have been achieved in high energy heavy ion collisions utilitizing the Relativistic Heavy Ion Collider at BNL: – a new phenomena – which was proven to signal a new state of matter – this state of matter was found to be a perfect fluid, with temperatures reaching 2 terakelvins and more – the degrees of freedom were shown to be the quarks – and the kinematic viscosity of this matter at extemely high temperatures were found to be less than that of a superfluid 4He at the onset of superfluidity. I will summarize these milestones and some more recent novel results of the RHIC programme and also outline an interesting new direction,

Anthropy and entropy – Irit Maor Tue. November 25th, 2008
11:30 am-12:30 pm

TBA

On the Challenge to Unveil the Microscopic Nature of Dark Matter – Scott Watson Tue. November 18th, 2008
11:30 am-12:30 pm

Despite the successes of modern precision cosmology to measure the macroscopic properties of dark matter, its microscopic nature still remains elusive. LHC is expected to probe energies relevant for testing theories of electroweak symmetry breaking, and as a result may allow us to produce dark matter for the first time. Other indirect experiments, such as PAMELA, offer additional ways to probe the microscopic nature of dark matter through observations of cosmic rays. Results from a number of indirect detection experiments seem to suggest that our old views of the creation of dark matter may need revisited. This is also suggested by theories of electroweak symmetry breaking that are required to be well behaved at high energies and in the presence of gravity.

South Pole Telescope: From conception to first discovery – Zak Staniszewski Tue. October 21st, 2008
11:30 am-12:30 pm

The South Pole Telescope recently discovered three new galaxy clusters in their CMB maps via the Sunyaev Zel’dovich (SZ) effect (Staniszewski et al. 2008). These are the first galaxy clusters discovered using this promising new technique. The number of galaxy clusters at a given redshift depends strongly on the expansion history of the universe as well as the relative abundances of matter, dark matter and dark energy during structure formation. The brightness of the SZ signal from a galaxy cluster is nearly redshift independent, making it a powerful tool for discovering galaxy clusters that were forming when dark energy was becoming important.

Primordial Nongaussianity and Large-Scale Structure – Dragan Huterer Fri. October 17th, 2008
11:30 am-12:30 pm

The near-absence of primordial nongaussianity is one of the basic predictions of slow roll, single-field inflation, making measurements of nongaussianity fundamental tests of the physics of the early universe. I first review parametrizations of nongaussianity and briefly review the history of its measurements from the CMB and large-scale structure. I then present results from recent work where effects of primordial nongaussianity on the distribution of largest virialized objects was studied numerically and analytically. We found that the bias of dark matter halos takes strong scale dependence in nongaussian cosmological models. Therefore, measurements of scale dependence of the bias, using various tracers of large-scale structure,

In Search of the Coolest White Dwarfs – Evalyn I.Gates Tue. October 14th, 2008
11:30 am-12:30 pm

Cool white dwarf stars are among the oldest objects in the Galaxy. These relics of an ancient stellar population offer a window into the early stages of the galaxy and its formation, and more data on the oldest and coolest white dwarfs may help resolve the interpretation of microlensing searches for MACHOs in the galactic halo. The Sloan Digital Sky Survey (SDSS) and the SEGUE program of SDSS-II are ideally suited to a search for these rare objects, and to date we have discovered 13 new ultracool white dwarfs =96 those with temperatures below 4000K =96 constituting the majority of these faint stellar fossils.

The White Elephant: Upsilon Physics at the BaBar B-factory – Steve Sekula Tue. October 7th, 2008
11:30 am-12:30 pm

For a decade, the PEP-II/BaBar B-factory has been a flagship experiment in precision measurements in the flavor sector, notably in the decays of B and charm mesons. Before its shutdown in April, the B-factory took a new direction and secured the world’s largest samples of Upsilon(3S) and Upsilon(2S) mesons and performed an extensive scan above the Upsilon(4S) resonance. I will talk about the motivation for this change of course and our new results in both the search for the ground state of bottomonium and the search for evidence of new physics at a low mass scale, including both the Higgs and dark matter.

Parameterizing dark energy – Zhiqi Huang Tue. September 16th, 2008
11:30 am-12:30 pm

Dark energy is parameterized by the time evolution of its equation of state $w(z)$. For a very wide class of quintessence (and phantom) dark energy models, we parameterize $w(z)$ with physical quantities related to the scalar field potential and initial conditions. Using a set of updated observational data including supernova, CMB, galaxy power spectrum, weak lensing and Lyman-${\alpha}$ forest, we run Markov Chain Monte Carlo calculations to determine the likelihood of cosmological parameters including the new dynamical parameters. The best fit model is centered around the cosmological constant (flat potential), while many popular scalar field models are excluded at different levels.

The effect of dark matter halos on reionization and the H21 cm line – Aravind Natarajan Fri. September 5th, 2008
11:30 am-12:30 pm

If much of the dark matter in the Universe consists of WIMPs, their annihilation releases energy, some of which ionizes the IGM. We calculate the contribution to the optical depth due to particle annihilation in early halos. This allows us to place bounds on the dark matter particle mass. We also consider the effect of halos on the H21 cm background. It is shown that larger halos (~ 10^6 solar masses) contain enough hot Hydrogen gas to produce a measurable H21 cm background. We present our conclusions.

Probing dark energy with cosmology – Roberto Trotta Tue. May 6th, 2008
11:30 am-12:30 pm

In order to pin down the fundamental nature of dark energy, and thus to understand what most of the Universe is actually made of, new and more precise observations are required, along with more efficient and reliable statistical techniques to interpret those observations correctly and to understand the implications they have for our theoretical models of the Universe. The outstanding challenge posed by the nature and properties of dark energy is giving rise to a flourishing of proposals for new observational campaigns. Type Ia supernovae, gravitational lensing, cluster counts and baryonic acoustic oscillations are some of the techniques available to study dark energy,

Astrophysics and Particle Physics with IceCube – Tyce DeYoung Tue. April 8th, 2008
11:30 am-12:30 pm

The IceCube neutrino observatory under construction at the South Pole is designed to detect high energy (TeV-PeV) neutrino emission from astrophysical objects, such as the sources of galactic and extragalactic cosmic rays. Data is being taken with the partially- built detector, now half complete with 40 strings and 2400 optical modules, and initial results are now available. In addition to astrophysical studies, IceCube also has a broad particle physics program that will be enhanced by the addition of the IceCube Deep Core, a dense, contained subarray that will push IceCube’s energy reach down to 10-20 GeV and improve its sensitivity to dark matter,

UHECR Phenomenology – Glennys Farrar Tue. March 18th, 2008
11:30 am-12:30 pm

I will review some very general properties that must characterize any relativistic UHECR accelerator, and I will list some key observational constraints on the accelerators. In combination these make it unlikely that any of the conventional source candidates can be solely responsible for the observed cosmic rays about about 60 EeV. I will describe a recently proposed new mechanism that is in excellent accord with the constraints and observations. I will describe how it can be tested using UHECRs and GLAST.

Challenging the Cosmological Constant – Nemanja Kaloper Thu. February 28th, 2008
11:30 am-12:30 pm

We outline a dynamical dark energy scenario whose signatures may be simultaneously tested by astronomical observations and laboratory experiments. The dark energy is a field with slightly sub-gravitational couplings to matter, a logarithmic self- interaction potential with a scale tuned to ~ 10 -3 eV, as is usual in quintessence models, and an effective mass m phi influenced by the environmental energy density. Among the signatures of this scenario may be dark energy equation of state w is not equal to -1, stronger gravity in dilute mediums, that may influence BBN and appear as an excess of dark matter, and sub- millimeter corrections to Newton’s law,

Observing Dark Energy with the Next Generation of Galaxy Surveys – Ofer Lahav Tue. February 26th, 2008
11:30 am-12:30 pm

The talk will discuss the design and forecasting for measuring properties of Dark Energy and Dark Matter from new deep imaging surveys, in particular the “Dark Energy Survey” and the DUNE satellite. The effect of accuracy of photometric redshifts on the cosmological results will be assessed.

k-Essence: superluminal propagation, causality and emergent geometry – Alexander Vikman Tue. February 19th, 2008
11:30 am-12:30 pm

K-essence models – scalar field theories with non-quadratic kinetic terms – are considered candidates for dynamical dark energy and inflation. One of the most interesting features of these nonlinear theories is that perturbations around nontrivial backgrounds propagate with a speed different from the speed of light. In particular, superluminal propagation is possible. In my talk, I will review the k-essence paradigm emphasizing the issues related to causality. I will show that superluminal propagation does not lead to any additional causal paradoxes over and above those already present in standard general relativity. I will end by presenting a model which allows the obtaining of information from beyond the horizon of a black hole.

Physics Beyond the Horizon – Niayesh Afshordi Tue. February 12th, 2008
4:30 pm-5:30 pm

The history of human knowledge is often highlighted by our efforts to explore beyond our apparent horizon. In this talk, I will describe how this challenge has now evolved into our quest to understand the physics at/beyond the cosmological horizon, some twenty orders of magnitude beyond Columbus’s original plan. I also argue why inflationary paradigm predicts the existence of non-trivial physics beyond the cosmological horizon, and how we can use the Integrated Sachs-Wolfe effect in the Cosmic Microwave Background to probe this physics, which includes the nature of gravity and primordial non-gaussianity on the horizon scale.

Demystifying the Large-Scale Structure and Evolution of the Cosmos – Constantinos Skordis Tue. February 5th, 2008
11:30 am-12:30 pm

In the last two decades, cosmology has undergone a revolution, with a large influx of high quality data. There is now a consensus cosmological standard model, Lambda-CDM, based on General Relativity as the theory of gravity, and which requires only about 4% of the energy budget of the universe to be in known baryonic form. The rest is divided into two apparently distinct, dark components: Cold Dark Matter (CDM) and cosmological constant. The simplest explanation for CDM is a weakly interacting particle, still to be detected; he cosmological constant is the simplest term that can be added to the Einstein equations that can give rise to the observed accelerated expansion of the universe but has no compelling explanation within our current understanding of fundamental physics.

Cosmological Unification of String Theories – Simeon Hellerman Fri. January 18th, 2008
1:00 pm-2:00 pm

Recent developments have greatly extended our understanding of quantum gravity in cosmological environments. A new set of exact time-dependent solutions has been found to the equations of motion of string theory, that interpolate among string theories of dramatically different character. These transitions dynamically alter features of the theory such as the degree of stability, the amount of supersymmetry, the number of dimensions of space itself, and the basic type of string. Taken together, these transitions fill out a web that unifies (almost) all known string theories into a single dynamical structure.

The Accelerating Universe: Landscape or Modified Gravity? – Sergei Dubovsky Tue. January 15th, 2008
4:30 pm-5:30 pm

The most remarkable recent discovery in fundamental physics is that the Universe is undergoing accelerated expansion. To achieve a proper understanding of its physical origin forces us to make a hard choice between dynamical and enviromental scenarios. The first approach predicts the existence of a new long distance physics in the gravitational sector, while the second relies on the existence of the vast landscape of vacua with different values of the cosmological constant. I will discuss achievements and shortcomings of each of the approaches, and illustrate them in the concrete examples.

Late Time Behavior of False Vacuum Decay – James Dent Fri. December 7th, 2007
12:30 pm-1:30 pm

The late time behavior of decaying states is examined with regards to its deviation from the usual exponential form of decay. We will look at the origins of this well-established result in quantum mechanics and discuss the issues that arise in a field theory setting. An increase in the survival probability of a metastable state at large times finds applications in the context of cosmology, namely with regards to eternal inflation and the string theory landscape.

What do WMAP and SDSS really tell about inflation? – Wessel Valkenburg Tue. December 4th, 2007
11:30 am-12:30 pm

We present new constraints on the Hubble function H(phi) and subsequently on the inflationary scalar potential V(phi) from WMAP 3-year data combined with the Sloan Luminous Red Galaxy survey (SDSS-LRG), using a new methodology which appears to be more generic, conservative and model-independent than in most of the recent literature, since it depends neither on the slow-roll approximation, nor on any extrapolation scheme for the potential beyond the observable e-fold range, nor on additional assumptions about initial conditions for the inflaton velocity. Besides these new constraints, we will briefly discuss the accuracy of the slow-roll approximation in the light of present day observations,

Bekenstein-Sanders theory of modified gravity – Constantinos Skordis Tue. November 27th, 2007
11:30 am-12:30 pm

TBA

Gravitational Radiation from Supermassive Black Hole Binaries – Andrew Jaffe Tue. November 20th, 2007
11:30 am-12:30 pm

Evidence for Supermassive Black Holes at the centers of galaxy bulges, combined with the paradigm of hierarchical structure formation, implies the existence of binary Supermassive Black Holes. It is expected that these binaries themselves will eventually coalesce in what would be the brightest gravitational-radiation events in the astrophysical universe. In this talk, we discuss the effect of the overall galaxy merger rate as well as dynamical processes at the centers of galaxies that might effect this scenario, in particular the so-called “final parsec problem” indicating that a significant fraction of the binaries may stall before they can coalesce. I discuss the theoretical prospects for resolving this problem,

Scanning Inflation – Pascal Vaudrevange Tue. November 20th, 2007
11:30 am-12:30 pm

The shapes of the primordial power spectra are the key quantities to unravel the physics of the inflationary epoch. We propose a new framework for parametrizing the spectra of primordial scalar and tensor perturbations, stressing the statistical trajectory nature of the relevant quantities and the importance of priors which can lead to spurious results like an apparent detection of tensor modes. We clarify the impact of prior probabilities, demonstrate strategies to adjust the prior distributions and as an example investigate a model inspired by high energy theory that exhibits intrinsic statistical elements.

Sterile neutrinos as subdominant warm dark matter – Dan Cumberbatch Tue. November 13th, 2007
11:30 am-12:30 pm

In light of recent findings which seem to disfavor a scenario with (warm) dark matter entirely constituted of sterile neutrinos produced via the Dodelson-Widrow (DW) mechanism, my colleagues and I investigated the constraints attainable for this mechanism by relaxing the usual hypothesis that the relic neutrino abundance must necessarily account for all of the dark matter. We firstly studied how to reinterpret the limits attainable from X-ray non-detection and Lyman-alpha forest measurements in the case that steril e neutrinos constitute only a fraction ‘f_s’ of the total amount of dark matter. Then, assuming that sterile neutrinos are generated in the early universe solely through the DW mechanism,

Baryogenesis, Electric Dipole Moments, and the Higgs Boson – Michael Ramsey-Musolf Tue. October 30th, 2007
11:30 am-12:30 pm

Explaining the predominance of visible matter over antimatter remains one of the outstanding puzzles at the interface of cosmology with particle and nuclear physics. Although the Standard Model cannot account for the matter-antimatter asymmetry, new physics at the electroweak scale may provide the solution. In this talk, I discuss the general requirements for successful electroweak scale baryogenesis; recent theoretical work in computations of the matter-antimatter asymmetry; and implications for experimental searches for permanent electric dipole moments of the electron and neutron and for the Higgs boson at future colliders.

Gravitational Breakthrough or Experimental Error? – Martin Tajmar Wed. October 24th, 2007
11:30 am-12:30 pm

Accelerometer measurments indicate that a circular field is induced when the rotation rate of a Niobium superconducting ring changes. If found to be genuine, this would be the first-ever gravitational-like field induced by controllable means. The field is measured inside the ring and its magnitude and direction opposes the ring’s angular acceleration. Since this observation does not match any theory, the emphasis is to carefully verify the observations. This seminar will describe the observations, experimental methods, and next-step options. This includes data from independent experiments conducted at the University of Canterbury, NZ, where the world’s most accurate ring-laser-gyro was used to search for the noted effects,

Extragalatic Cosmic Rays: a Prescription to Avoid Disaster – Corbin Covault Tue. October 16th, 2007
11:30 am-12:30 pm

The origin of the highest energy cosmic rays has remained a persistent mystery for decades. Now we seem to be on the verge of getting a new handle on where in the universe these things come from. The Pierre Auger Observatory has been operating since 2004, and already we have some clear clues, including the energy spectrum and limits on photon flux that strongly suggest an extragalactic origin for the highest energy cosmic rays. More recently the unparalleled collecting area of Auger has been brought to bear on the question of potential correlations between particular astrophysical objects and cosmic ray arrival directions.

Dark matter, small-scale structure, and dwarf galaxies – Louie Strigari Tue. September 4th, 2007
11:30 am-12:30 pm

The standard model of cold dark matter predicts the existence of thousands of small dark matter halos orbiting the Milky Way, and steep cusps in the central regions of dark matter halos. The low-luminosity, dark matter dominated dwarf galaxy population of the Milky Way provides an ideal laboratory for testing these predictions, and thus placing strong constraints on the nature of dark matter. I will show how present kinematic data from the galaxies tests solutions to the CDM ‘missing satellites problem,’ and how future astrometric data will reveal the presence of central density cores or cusps. I will also discuss how the kinematic data from these galaxies is able to provide strong constraints on the signal from cold dark matter particles annihilating into gamma-rays,

String Gas Cosmology and Structure Formation – Robert Brandenberger Tue. April 24th, 2007
11:30 am-12:30 pm

Understanding the very early universe is linked inextricably with understanding the resolution of cosmological singularities. I will discuss “string gas cosmology”, one of the approaches making use of string theory to obtain an improved picture of the early universe cosmology. In particular, I will show that string gas cosmology can lead to a new structure formation scenario in which string thermodynamic fluctuations generate a scale-invariant spectrum of adiabatic fluctuations.

The Origin of the Big Bang: the status of inflation after WMAP – Slava Mukhanov Fri. April 20th, 2007
11:30 am-12:30 pm

I will discuss at a colloquium level the robust model independent predictions of inflation and compare these predictions with the results of the observations of the fluctuations of the cosmic mictrowave background radiation.

Prospects for a New Type of High Energy Physics Facility: a Muon Collider – Tom Roberts Fri. April 13th, 2007
11:30 am-12:30 pm

In a few years, after Fermilab’s Tevatron turns off and initial LHC results are available, the High Energy Physics community will be at a crossroads: what type of facility to consider next? Neither proton nor electron machines hold much prospect for advancing the energy frontier beyond the LHC. But recent innovations in manipulating muon beams make it possible to imagine a third type of facility for HEP: a muon collider. An energy frontier muon collider could potentially fit on the Fermilab site, opening a completely new window into fundamental particle processes. In addition to presenting the basic concept, this talk will discuss the challenges inherent in creating,

Ongoing Mysteries in Astrophysics – Don Driscoll Wed. April 11th, 2007
4:00 pm-5:00 pm

We are at the brink of a Golden Age of Astrophysics with the promise of answers to many long-outstanding questions, including: What is the nature of Dark Matter? What source powers Active Galactic Nuclei? Where do Gamma-Ray Bursts come from? Where do the highest energy Cosmic Rays come from? With an unprecedented number of experiments both active and coming online, there is a real hope that many of these questions may be answered in the near future. I have been lucky enough to be associated with some of the world’s most advanced astrophysical experiments. In this talk, I plan on detailing my life as an experimentalist and how my work has touched on some of these intriguing questions.

Probability in cosmology: from Bayes theorem to the anthropic principle – Roberto Trotta Tue. March 27th, 2007
11:30 am-12:30 pm

TBA

EBEX, a CMB B-mode polarization experiment – Tomotake Matsumura Tue. March 20th, 2007
11:30 am-12:30 pm

I present a balloon-borne cosmic microwave background (CMB) polarization experiment, E and B experiment(EBEX). EBEX is designed, i) to detect or set an upper limit (T/S less than 0.03) on the inflationary gravity-wave background polarization anisotropy signal (primordial B-mode), ii) to measure the CMB polarization anisotropy signal induced by gravitational lensing (lensing B-mode), and iii) to measure galactic dust emission (120 GHz – 450 GHz) in order to monitor foreground contamination. In this talk, I present the EBEX science goals as well as an instrument overview. In particular among a number of subsystems in EBEX, I discuss a half-wave plate polarimeter using a superconducting magnetic bearing.

Warped Passages: Unravelling the Mysteries of the Universe’s Hidden Dimensions Tue. March 20th, 2007
5:30 pm-6:30 pm

Host: NOTE: The event is free, but registration is required, at www.case.edu/events/dls/register.html

Voids of Dark Energy – Sourish Dutta Tue. March 6th, 2007
11:30 am-12:30 pm

The present-day acceleration of the Universe is one of the greatest mysteries of modern cosmology. In the framework of general relativity, the expansion could be caused by either a “cosmological constant”, or a dynamical dark energy component (DDE). In this talk I will describe a novel theoretical approach to distinguishing between these two possibilities, namely, via the clustering properties of DDE. By following the dynamical evolution of matter perturbations in a cosmic mix of matter and DDE, we find the very interesting result that the DDE tends to form voids in the vicinity of gravitationally collapsing matter. I will discuss these voids in detail,

Reconstructing dark energy using Maximum Entropy – Caroline Zunckel Fri. March 2nd, 2007
12:30 pm-1:30 pm

Even in what has been termed an age of `precision cosmology’ certain anomalies on a range of astrophysical scales are observed and demand the existence of unseen types of matter or modifications to our current gravitational theory. In this article the issue of the nature of the mysterious `dark energy’ has been explored in a model-independent way. A maximum-entropy technique is developed and used to reconstruct the equation of state of dark energy within a bayesian framework. The motivation for the use of the MaxEnt technique is the lack of good data points in comparison to the number of parameters required for a sufficient characterization of dark energy.

Do quantum excitations of the inflaton decay? – Cristian Armendariz-Picon Fri. February 16th, 2007
12:30 pm-1:30 pm

The properties of the primordial perturbations seeded during a stage of inflation are determined by the quantum state of the inflaton. This state is usually assumed to be the “vacuum”, since one expects excited states to decay into the state of lowest energy. In the talk I discuss whether this assumption holds in the presence of a short-distance cut-off. I describe the calculation of transition probabilities between excited states and the vacuum, and discuss the implications of the results that I obtain.

Cosmic (super)strings: Gravitational wave bursts, stochastic background, and experimental constraints – Xavier Siemens Tue. January 30th, 2007
11:30 am-12:30 pm

I discuss gravitational wave experimental signatures (bursts and stochastic background) of cosmic strings. I will show burst rates that are substantially lower (about a factor of 1000) than previous estimates suggest and explain the disagreement. Initial LIGO is unlikely to detect bursts from field theoretic cosmic strings, though it may detect cosmic superstring bursts. I also compare the stochastic background produced by a network of strings with a wide range of experiments and indirect bounds. If the latest cosmic string simulation results are correct then a large area of superstring parameter space is ruled out by pulsar timing observations.

Quantum cosmology and the conditions at birth of the universe – Serge Winitzki Tue. January 23rd, 2007
11:30 am-12:30 pm

Cosmology ultimately aims to explain the initial conditions at the beginning of time and the entire subsequent evolution of the universe. The “beginning of time” can be understood in the Wheeler-DeWitt approach to quantum gravity, where homogeneous universes are described by a Schroedinger equation with a potential barrier. Quantum tunneling through the barrier is interpreted as a spontaneous creation of a small (Planck-size) closed universe, which then enters the regime of cosmological inflation and reaches an extremely large size. After sufficient growth, the universe can be adequately described as a classical spacetime with quantum matter. The initial quantum state of matter in the created universe can be determined by solving the Schroedinger equation with appropriate boundary conditions.

The life and death of dark matter halos: predictions for neutralino annihilation Tue. December 12th, 2006
11:30 am-12:30 pm

The concordance cosmological model predicts that structures in the Universe form via hierarchical merging, beginning with the smallest dark matter mini-halos. The mass of the smallest halo is set by the initial thermal motion of dark matter particles. After merging into larger systems and subsequent dynamical evolution, most halos lose between 50% and 99% of their mass but an interesting fraction of dark matter remains in self-bound clumps at all mass scales. The smallest substructure has important implications for the detection of dark matter annihilation, predicted by SUSY models.

Aethereal Gravity – Brendan Foster Tue. December 5th, 2006
11:30 am-12:30 pm

Hints from quantum gravity suggest the existence of a preferred frame. One way to accommodate such a frame in general relativity without sacrificing general covariance is to couple the metric to a dynamical, timelike, unit-norm vector field–the “aether”. I will discuss observational constraints on a class of such theories, with a focus on post-Newtonian effects and radiation from binary pulsar systems, and show that a subset remains viable.

The Quintessence Potential: Need for Features and Tracking? – Martin Sahlen Tue. November 28th, 2006
11:30 am-12:30 pm

We reconstruct the potential of a quintessence field from current observational data, including new supernova data, plus information from the cosmic microwave background and from baryon acoustic oscillations. We model the potential using Pade approximant expansions as well as Taylor series, and use observations to assess the viability of the tracker hypothesis. Present data provide some insights into the shape of a presumptive quintessence potential, but also strengthen the model selection preference for the cosmological constant over evolving models. They also show some signs, though inconclusive, of favouring tracker models over non-tracker models under our assumptions.

Exploring the Dark Energy Domain – Dragan Huterer Tue. November 21st, 2006
11:30 am-12:30 pm

One of the great mysteries of modern cosmology is the origin and nature of dark energy – a smooth component that contributes about 70% of the total energy density in the universe and causes its accelerated expansion. Here I present results from a comprehensive study of a class of dark energy models, exploring their dynamical behavior using the method of flow equations and the Monte Carlo Markov Chain machinery that have previously been applied to inflationary models. I comment on the current and expected future constraints, insights into the dynamics of dark energy, figures of merit, and a classification of theoretical models.

Probing Dark Energy – Josh Frieman Tue. November 14th, 2006
11:30 am-12:30 pm

TBA

Black Hole Formation, Evaporation and the Information Loss Problem – Dejan Stojkovic Tue. October 17th, 2006
11:30 am-12:30 pm

We use the full quantum treatment to study formation of a black hole as seen by an asymptotic observer. Using the Wheeler-de Witt equation to describe a collapsing shell of matter (a spherical domain wall), we show that the black hole takes an infinite time to form in the quantum theory, just as in the classical treatment. Asymptotic observers will therefore see a compact object but never see effects associated with an event horizon. To explore what signals such an observer would see we study radiation of quantum fields in this background using two approaches: functional Schroedinger method and an adaptation of Hawking’s original calculation.

Nuclear astrophysics underground – Heide Costantini Tue. October 3rd, 2006
11:30 am-12:30 pm

Cross section measurements for quiescent stellar burning are hampered mainly by extremely low counting rate and cosmic background. Some of the main reactions of H-burning phase have been measured at the LUNA facility (Laboratory for Underground Nuclear Astrophysics) taking advantage of the very low background environment of the Underground Gran Sasso National Laboratory in Italy. The adopted experimental techniques will be presented together with the latest results on the 14N(p,g)15O reaction and the status of the ongoing 3He(4He,g)7Be experiment. Furthermore a brief overview of the ALNA (Accelerator Laboratory for Nuclear Astrophysics underground) project, as a part of the new future Underground DUSEL laboratory in the USA,

Searching for double beta decay with the Enriched Xenon Observatory – Carter Hall Tue. September 26th, 2006
11:30 am-12:30 pm

Neutrinoless double beta decay has recently become a top priority for the global experimental neutrino physics program. Double beta decay has the potential to resolve the scale of the neutrino mass spectrum, and is also the only practical tool we have for understanding the particle/anti- particle nature of the neutrino. The Enriched Xenon Observatory (EXO) collaboration is developing sensitive searches for the double beta decay of Xenon-136. Our first experiment, EXO-200, will be the largest double beta decay experiment ever attempted by an order-of-magnitude, and is rapidly being constructed. We are also pursuing R and D to realize a system to tag the daughter barium nucleus of the decay using the techniques of single-ion spectroscopy.

Positron annihilations at the Galactic Center: Generating more questions than answers – Hasan Yuksel Tue. September 26th, 2006
11:30 am-12:30 pm

The bulge of our Galaxy is illuminated by the 0.511 MeV gamma-ray line flux from annihilations of nonrelativistic positrons. The emission is strongly concentrated at the Galactic Center, in contrast to gamma-ray maps tracing nucleosynthesis (e.g., the 1.809 MeV line from decaying ^26Al) or cosmic ray processes (e.g., the 1-30 MeV continuum), which reveal a bright disk with a much less prominent central region. Central to resolving the origin of the positrons is the question of their injection energies, which range up to 100 MeV or even higher in recent astrophysical and exotic (requiring new particle physics) models. If positrons are generated at relativistic energies,

Michelson Postdoctoral Prize Lecture – Nicole Bell Mon. May 1st, 2006
11:30 am-12:30 pm

Astrophysical Neutrinos: Revealing Neutrino Properties at the Highest Energies

Accelerated expansion from structure formation – Syksy Rasanen Tue. April 4th, 2006
11:30 am-12:30 pm

I discuss the backreaction of inhomogeneities on the expansion of the universe. The average behaviour of an inhomogeneous spacetime is not given by the Friedmann-Robertson-Walker equations. The new terms in the exact equations hold the possibility of explaining the observed acceleration without a cosmological constant or new physics. In particular, the coincidence problem may be solved by a connection with structure formation.

DEAP and CLEAN Detectors for Low-Energy Particle Astrophysics – Andrew Hime Tue. March 7th, 2006
11:30 am-12:30 pm

The unique properties of scintillation light in liquid neon and liquid argon make possible conceptually simple, massive, and highly sensitive detectors of low-energy solar neutrinos and cosmological dark matter. I will describe the program underway for the design and construction of two novel and complementary detectors dubbed DEAP (Dark matter Experiment with Argon and Pulse shape discrimination) and CLEAN (Cryogenic Low Energy Astrophysics with Neon).

In Search of Particle Dark Matter – Dan Hooper Tue. February 28th, 2006
11:30 am-12:30 pm

In recent years, we have learned a great deal about dark matter, but are still ignorant of its identity. The key to uncovering this mystery is likely to lie in some combination of direct and indirect detection techniques, as well as with collider experiments. In this talk, I will explore the ability of indirect detection experiments using anti-matter, neutrinos and gamma-rays to detect particle dark matter. I will summarize the current observational situation and project the reach of these endeavors in the coming years.

Galaxy Clustering in the SDSS Redshift Survey – Idit Zehavi Tue. February 21st, 2006
11:30 am-12:30 pm

The ongoing Sloan Digital Sky Survey (SDSS) is providing a wealth of information enabling extensive large-scale structure studies. I will present measurements of galaxy clustering with the SDSS redshift survey, using a sample of about 200,000 galaxies, and concentrating on the two-point correlation function. The SDSS is particularly suitable for investigating the dependence of clustering on galaxy properties, and we focus on the dependence on color and on luminosity. We interpret the measurements using contemporary models of galaxy clustering, which help to elucidate the features of the observed correlation functions and provide insights on galaxy formation and the relation of galaxies and dark matter.

Cosmogenic Radioisotopes in Low Background Experiments – The WARP Experiment at Gran Sasso – Cristiano Galbiati Tue. January 24th, 2006
11:30 am-12:30 pm

I will discuss results from recent studies on production of radioisotopes by muon-induced showers in neutrino detectors located deep underground. Cosmogenic radioisotopes represent one of the most significant and important classes of background for experiments on solar neutrinos. I will show how a detailed understanding of the production mechanisms of the radioisotopes can help in opening new windows of observation for low energy solar neutrinos (in particular, pep neutrinos). I will also review the status and the plans for the WARP experiment at Gran Sasso. WARP is a two-phase argon drift chamber designed for direct detection of WIMP Dark Matter.

TeV gamma-rays and the largest masses and annihilation cross sections of neutralino dark matter – Stefano Profumo Tue. November 15th, 2005
11:30 am-12:30 pm

Motivated by the interpretation of the recent results on the TeV gamma radiation from the Galactic center, including the new 2004 HESS data, as a by-product of dark matter particles annihilations, we address the question of the largest possible neutralino masses and pair annihilation cross sections in supersymmetric models. Extending the parameter space of minimal models, such as the mSUGRA and the mAMSB scenarios, to general soft SUSY breaking Higgs masses gives access to the largest possible pair annihilation rates, corresponding to resonantly annihilating neutralinos with maximal gaugino-higgsino mixing. Adopting a model-independent approach, we provide analytical and numerical upper limits for the neutralino pair annihilation cross section.

Chaotic Processes in Planet Migration and Orbital Evolution – Fred Adams Tue. November 8th, 2005
11:30 am-12:30 pm

Nearly 150 extrasolar planets have been discovered to date, and their observed orbits display an unexpected diversity. This talk considers a collection of processes for planet migration and orbital evolution, including those operating on a range of time scales. In particular, we consider planet-planet scattering, the action of disk torques, scattering of solar systems with passing binary star systems, and the long term evolution of planetary systems. The result of this survey of processes provides a explanation for the orbital elements of observed planetary systems, places constraints on the birth aggregate of our solar system, and determines the fraction of binary star systems that allow for the long term stability of an Earth-like planet.

Prospects for Measuring nu-N Coherent Scattering at a Spallation Source Tue. October 18th, 2005
11:30 am-12:30 pm

Coherent neutral current neutrino-nucleus elastic scattering has never been observed. Although the cross-section is very high, nuclear recoil energies are very small. However, detection of the process may be possible for the new generation of low-threshold detectors. A promising prospect for the first detection of this process is an experiment at a high flux stopped-pion neutrino source such as the SNS. I will present some preliminary rate calculations and discuss the physics reach of such an experiment.

On virialization with dark energy – Irit Maor Tue. October 11th, 2005
11:30 am-12:30 pm

We review the inclusion of dark energy into the formalism of spherical collapse, and the virialization of a two-component system, made of matter and dark energy. We compare two approaches in the literature. The first assumes that only the matter component virializes, e.g. as in the case of a classic cosmological constant. The second approach allows the full system to virialize as a whole. We show that the two approaches give fundamentally different results for the final state of the system. This might be a differentiating signature between the classic cosmological constant which cannot virialize, and a dynamical dark energy mimicking a cosmological constant.

Prospects for Measuring nu-N Coherent Scattering at a Spallation Source – Kate Scholberg Tue. October 11th, 2005
11:30 am-12:30 pm

Coherent neutral current neutrino-nucleus elastic scattering has never been observed. Although the cross-section is very high, nuclear recoil energies are very small. However, detection of the process may be possible for the new generation of low-threshold detectors. A promising prospect for the first detection of this process is an experiment at a high flux stopped-pion neutrino source such as the SNS. I will present some preliminary rate calculations and discuss the physics reach of such an experiment.

Wormholes, Dark Energy, and the Null Energy Condition – Roman Buniy Tue. October 4th, 2005
11:30 am-12:30 pm

We show that violation of the null energy condition implies instability in a broad class of models, including classical gauge theories with scalar and fermionic matter as well as any perfect fluid. When applied to the dark energy, our results imply that w = p / rho is unlikely to be less than -1. As another application, Lorentzian (traversable) wormholes and time machines with semi-classical spacetimes are unstable to small perturbations.

Can black hole events from cosmic rays be observed at the Auger Observatory? – Dejan Stojkovic Tue. September 27th, 2005
11:30 am-12:30 pm

It has been argued that neutrinos originating from ultra-high energy cosmic rays produce black holes deep in the atmosphere in models with TeV-scale quantum gravity. Such black holes would initiate quasi-horizontal showers of particles far above the standard model rate, so that the Auger Observatory would observe hundreds of black hole events. This would provide the first opportunity for experimental study of microscopic black holes. However, any phenomenologically viable model with a low scale of quantum gravity must explain how to preserve protons from rapid decay mediated by virtual black holes. We argue that unless this is accomplished by the gauging of baryon or lepton number,

Quantum metric fluctuations in cosmological and black hole spacetimes – Albert Roura Tue. September 20th, 2005
11:30 am-12:30 pm

It is expected that a number of quantum aspects of the gravitational field and its interaction with the remaining matter fields can be studied within a low-energy effective field theory approach provided that the typical scales involved are much larger than the Planck length. This has been considered in some detail for weak gravitational fields, but physically interesting situations often involve strong fields. Some non-equilibrium field theory methods which are particularly useful to address gravitational back reaction problems, such as the closed time path (CTP) formalism, will be briefly reviewed. I will then explain how to extract information on metric fluctuations and discuss applications to black hole and cosmological spacetimes.

What is the Cosmological Significance of a Discovery of Wimps at Colliders or in Direct Experiments? – Jacob Bourjaily Tue. September 13th, 2005
11:30 am-12:30 pm

Although a discovery of wimps either at colliders or indirect experiments would have enormous implications for our understanding of particle physics, it would imply less than one would like about our understanding of the dark matter in the universe or in the galactic halo: it surely is possible that discovered particles account for only a little of the total dark matter. To establish the cosmological significance of a wimp discovery, their density must be determined. I will show that data from neither hadron colliders nor direct detection experiments alone can be sufficient to determine the local or relic density of discovered wimps,

Boundary Localized Symmetry Breaking and Topological Defects – Matthew Martin Fri. May 6th, 2005
11:30 am-12:30 pm

I discuss the structure of topological defects in the context of recent extra dimensional models where the symmetry breaking terms are localized. These defects develop structure in the extra dimension which differs from the case where symmetry breaking is not localized. This new structure can lead to corrections to the mass scale of the defects which is not captured by the effective theory obtained by integrating out the extra dimension. I also consider the Higgsless model of symmetry breaking and show that no finite energydefects appear in some situations where they might have been expected.

The Ages of the Oldest Stars – Brian Chaboyer Tue. April 26th, 2005
11:30 am-12:30 pm

The ages of the oldest stars in the Milky Way yield a reliable lower limit to the age of the universe and provide important information on the early formation history of our Galaxy. I will provide an overview of the stellar age determination process, including a critical look at the uncertainties associated with determining the ages of stars. Evidence for a significant spread in ages among the old stars in the halo of the Milky Way will be presented and used to study the early formation history of our Galaxy. I will conclude by discussing the absolute age of the oldest stars and its implications for cosmology.

Gravity and Horizon Entropy – Ted Jacobson Fri. April 8th, 2005
11:30 am-12:30 pm

I will argue that if (i) entanglement entropy density across any surface is a universal finite constant η, and (ii) local Lorentz symmetry holds, then the spacetime metric must satisfy the Einstein equation, with Newton’s constant equal to 1/(4 hbar η). I will then discuss the nature of black hole entropy in light of this result.

Technique for WIMP dark matter detection using pulse-shape discrimination in noble liquids – Mark Boulay Tue. March 29th, 2005
11:30 am-12:30 pm

It has long been known that a large fraction of our universe is composed of non-luminous or dark matter. The effects of dark matter have been observed since the 1930’s by studying velocity dipersions in galaxy clusters, and several direct searches for particle dark matter are ongoing. In this seminar I will present studies for the design of novel detectors for particle dark matter using scintillation pulse shape discrimination in noble liquids. Design of a dual-purpose liquid neon detector (CLEAN) for dark matter and low-energy solar neutrino interactions evaluated with Monte Carlo simulations will be discussed. The projected sensitivity for CLEAN is less than 10-46 cm2 for the spin-independent WIMP-nucleon cross-section,

Indirect signals from Dark Matter – Francesc Ferrer Fri. March 4th, 2005
11:30 am-12:30 pm

Abstract: The only evidence so far for the presence of Dark Matter in our Galaxy is through its gravitational interactions. Several experiments, however, have recently observed the emission of gamma-rays from the Galactic Center that could be caused by the annihilation of Dark Matter particles. Candidates with masses ranging from the MeV to the ZeV will be explored and constraints on their properties will be obtained by requiring that they account for the observed Galactic radiation.

A Geometric approach to Distinguish Between a New Source and Random Fluctuations: Applications to High-Energy Physics – Ramani S. Pilla Fri. February 25th, 2005
11:30 am-12:30 pm

One of the fundamental problems in the analysis of experimental data is determining the statistical significance of a putative signal. Such a problem can be cast in terms of classical “hypothesis testing”, where a null hypothesis describes the background and an alternative hypothesis characterizes the signal as a perturbation of the background. This testing problem is often addressed by a chi- square goodness-of-fit or a likelihood ratio test (LRT) statistic. In general, the former does not yield good power in detecting the signal and the latter has lacked an analytically tractable reference distribution required to calibrate a test statistic. Pilla and Loader have introduced a new test statistic based on “perturbation theory”

Ultra-high energy neutrinos – Mike Duvernois Tue. February 22nd, 2005
11:30 am-12:30 pm

The search for GZK neutrinos, and its connection to the highest-energy cosmic rays will be discussed. In particular, we’ll look at the current generation of astrophysical and cosmological neutrino search experiments (Auger, Icecube, and ANITA) and the next generation of Terraton detectors for neutrino measurements.

CMB/LSS correlation as a probe of dark energy – Levon Pogosian Tue. February 15th, 2005
11:30 am-12:30 pm

Recent detection of the Integrated Sachs-Wolfe effect via cross-correlation of the CMB with large scale structure provided another piece of evidence for the existence of Dark Energy. Although cross-correlation measurements are limited by large statistical uncertainties, they probe physical processes that are only weakly constrained by the CMB spectra and the SNIa luminosity curves. I will show that the cross-correlation data, combined with the CMB power spectra, can provide competitive constraints on certain properties of dark energy.

Brane cosmology with an anisotropic bulk – Dani Steer Fri. February 11th, 2005
11:30 am-12:30 pm

In the context of brane cosmology, a scenario where our universe is a 3+1-dimensional surface (the “brane”) embedded in a five-dimensional spacetime (the “bulk”), we focus on geometries for which the brane is anisotropic though still homogeneous. The main question we address is the following: can an anisotropic brane be sourced by a perfect fluid? As opposed to standard 4D cosmology, we argue that this may only be possible for very specific perfect fluid sources.

The future of dark energy measurements – Dragan Huterer Tue. February 1st, 2005
11:30 am-12:30 pm

Evidence for the existence of some form of dark energy — a smooth component that causes the accelerated expansion of the universe and contributes about 70% of the total energy density — is by now very solid. However, despite thousands of published papers on the topic essentially no progress has been made in understanding its nature and the underlying physical mechanism. In this talk I describe the prospects of several methods to measure the macroscopic properties of dark energy within the next decade. In addition to type Ia supernovae, these include weak and strong gravitational lensing, number counts of clusters of galaxies,

Theoretical Constraints on the Dark Energy Equation of State – Mark Trodden Fri. January 28th, 2005
11:30 am-12:30 pm

Modern cosmological observations indicate that the expansion of the universe is accelerating. This is typically described in terms of the equation of state parameter of a hypothetical new component of the cosmic energy budget, presumed to be driving the acceleration. Observations then provide bounds on this parameter.

In this talk I will discuss theoretical limits on the values of this parameter. In the first part I will discuss the (dire) implications of inferring from the data that the equation of state parameter is less than -1. This may happen if cosmic acceleration is driven by an energy component that violates the energy conditions of general relativity.

Observing the Cosmic Infrared Background with Frequency Selective Bolometers – Thushara Perera Tue. November 30th, 2004
11:30 am-12:30 pm

TBA

Bayesian Analysis of the WMAP Data – Ben Wandelt Tue. November 16th, 2004
11:30 am-12:30 pm

The desire to solve the three cosmological conundra of dark matter, dark energy and initial conditions drives us to demand more from cosmological observations. We require methods that link observations to theory in a convenient and lossless way. I will discuss a Bayesian approach to the analysis of the cosmic microwave background that enables the statistically exact extraction of cosmological information from the CMB and present our results from applying this methodology to the first year of WMAP data.

Inflation, strings and the CMB – Ana Achucarro Tue. November 2nd, 2004
11:30 am-12:30 pm

In the last year there has been a sudden renewal of interest in cosmic (super)string networks. I will explain why and will discuss – in a non-technical way – some new cosmological models coming from superstring/supergravity theory, and how to constrain these models by their cosmic string production after inflation.

Possible evidence for spatial fluctuations in dark energy – Christopher Gordon Tue. October 26th, 2004
11:30 am-12:30 pm

The WMAP cosmic microwave background (CMB) first year data was anomalously smooth on the largest spatial scales. We have recently shown that spatial fluctuations in the dark energy, that is causing the expansion of the Universe to speed up, may partially cancel the fluctuations in the CMB on the largest scales. This would imply that the residual fluctuations that are observed on large scales would be due to the integrated Sachs Wolfe effect which is caused by the effect of large scale structure on the CMB at a redshift of about 1. We found that the current WMAP data provides a two sigma detection of the dark energy fluctuations.

Confronting Inflation with Observation – William Kinney Tue. October 19th, 2004
11:30 am-12:30 pm

Inflationary cosmology is a compelling model for the early universe, but until recently it has not been subject to precise experimental test. In the last year, new observations have made it possible not only to test the general predictions of inflation, but also to distinguish among (and rule out) particular models of inflation. I will discuss the status of inflationary cosmology in light of the most recent observations, and summarize what we can expect over the next few years.

Physics of the black hole-brane interaction – Dejan Stojkovic Tue. October 12th, 2004
11:30 am-12:30 pm

In models with extra dimensions that accommodate a TeV-scale gravity, small black holes that can be described by classical solutions of Einstein’s equations can exist. We study interaction of such black holes with our world — a brane embedded in a higher dimensional space. In such a setup there exist a host of new phenomena that do not have analogs in usual 3+1-dim models. We specially discuss experimental signature which may help us distinguish between the various extra dimensional scenarios.

Racetrack Inflation – Jose Blanco-Pillado Sat. October 9th, 2004
11:30 am-12:30 pm

Four dimensional effective actions of many of the currently studied extra-dimensional theories seem to contain massless scalar fields called moduli. Giving these fields a potential is crucial to make these theories compatible with observations. It is therefore natural to explore the possibility that before they settle down to the true minimum of their potentials these fields could be relevant for cosmology, in particular they could be the source of an inflationary expansion period of the universe. In this talk, I will review ealier attempts to follow these ideas and present a new model of topological modular inflation in the context of the recently develop flux compactifications within string theory.

First Results from the CAPMAP Experiment – Phil Farese Tue. September 28th, 2004
11:30 am-12:30 pm

CAPMAP is a dedicated 40 and 90 GHz CMB polarization experiment. Observing with a 7m radio telescope from Holmdale, NJ CAPMAP intends to measure the primary polarization of the CMB at small (60′-4′) angular scale where the signal is maximum. I will discuss the design of the experiment, results from its first season, and the full observing campaign intended to culminate this academic year.

Affleck-Dine Leptogenesis Induced by the Flaton of Thermal Inflation – Wan-il Park Tue. September 14th, 2004
11:30 am-12:30 pm

We propose a simple model in which MSSM plus neutrino mass term, (LH_u)^2 is supplemented by a minimal flaton sector to drive the thermal inflation, and make two crucial assumptions: the flaton vacuum expectation value generates the mu-term of the MSSM and m_L^2 +m_{H_u}^2<0. We show that our model leads to thermal inflation followed by Affleck- Dine leptogenesis along the LH_u flat direction.

Results from the Sudbury Neutrino Observatory Salt Phase and the Future of the SNO Detector – Darren Grant Tue. September 7th, 2004
11:30 am-12:30 pm

The Sudbury Neutrino Observatory is a heavy water Cherenkov detector designed to be sensitive to the total flux of Boron- 8 solar neutrinos. The addition of NaCl to the detector enhances the Neutral Current signal, and therefore improves the measurement of the total solar flux. The open salt dataset, consisting of approximately 254 days of livetime, has been analysed using analytic probabiltiy density functions in an extented maximum likelihood calculation. The final Boron-8 model constrained result of this analysis give a Charged Current to Neutral Current ratio of 0.344 +/- 0.021(stat) +0.024/-0.035(syst). This talk will present an overview of this independent analysis of the SNO data.

BPS bounds of F- versus D-term strings and their cosmological implications – Filipe Freire Tue. August 24th, 2004
11:30 am-12:30 pm

Supersymmetry seems to facilitate the bringing together of inflationary models with particle physics. We give an overview of inflation models in supersymmetric theories. These models often lead to the production of cosmic strings after inflation. The cosmological implication of the production of these strings strongly depends on whether they saturate the so-called BPS condition. We study a particular model where we show that the BPS condition is preserved at the quantum level. Do not be discouraged by some technical language used in the abstract, all that will hopefully be made clear in more physically transparent terms during the seminar.

Solar Evidence for Neutrino Transition Magnetic Moments and Sterile Neutrinos – David Caldwell Fri. July 9th, 2004
1:30 pm-2:30 pm

While KamLAND apparently rules out Resonant-Spin-Flavor-Precession (RSFP) as an explanation of the solar neutrino deficit, the solar neutrino fluxes in the Cl and Ga experiments appear to vary with solar rotation. Added to this evidence, summarized here, a power spectrum analysis of the Super-Kamiokande (SK) data reveals significant variation in the flux matching a dominant rotation rate observed in the solar magnetic field in the same time period. Four frequency peaks, all related to this rotation rate, can be explained quantitatively. A recent SK paper reported no time variation of the flux, but showed the same peaks with statistically insignificant sensitivity,

The Atacama Cosmology Telescope Project – Arthur Kosowsky Fri. June 11th, 2004
2:00 pm-3:00 pm

The Atacama Cosmology Telescope (ACT) is a custom-designed 6-meter microwave telescope employing superconducting bolometer array detectors, which will be located in the Atacama Desert of the Chilean Andes in 2006. It will provide maps of the cosmic microwave background at arcminute resolution and micro-Kelvin sensitivity over a hundred square degrees of sky. I will review the scientific motivation for building this instrument, explain some of the technologies which are necessary, and discuss plans for complementary astronomical observations. We aim to compile a catalog of 1000 galaxy clusters and redshifts, selected by their distortions of the microwave background. ACT will provide insights into a wide range of topics including the primordial spectrum of density fluctuations,

Terrestrial Mini-Bang: Transmuting a Color Glass Condensate into Quark Gluon Plasma at RHIC – Raju Venugopalan Tue. April 20th, 2004
11:30 am-12:30 pm

The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory is currently completing run 5. We discuss some of the remarkable and unexpected results emerging from experiments on Gold-Gold collisions at the ultrarelativistic energies of RHIC as well as results from Deuteron-Gold and Proton-Proton collisions at the same energies. Together, they provide a compelling (if not completely understood) picture of

a) the quark-gluon matter produced at RHIC and, unexpectedly,
b) a description of the matter constituting the wavefunction of a high energy hadron as a Color Glass Condensate.
Octonions and Fermions – Corinne A. Manogue Wed. April 14th, 2004
2:30 pm-3:30 pm

Ten dimensional supersymmetric theories of physics such as superstring theory are at heart just higher dimensional generalizations of the Dirac equation. An enduring problem with these theories is how to reduce the spacetime dimension to the four we live in. I will describe a mechanism for reducing 10 spacetime dimensions to 4 without compactification, based on a generalization of the complex numbers known as the octonions. Applying this mechanism to the 10-dimensional Dirac equation leads to a treatment of both massive and massless particles on an equal footing. The resulting unified description has the correct particle spectrum to describe precisely 3 generations of leptons,

Exoplanets, The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way – Charley Lineweaver Wed. April 7th, 2004
2:30 pm-3:30 pm

As we learn more about the Milky Way Galaxy, extrasolar planets and the evolution of life on Earth, qualitative discussions of the prerequisites for life in a Galactic context can become more quantitative. We model the evolution of the Milky Way Galaxy to trace the distribution in space and time of four prerequisites for complex life: the presence of a host star, enough heavy elements to form terrestrial planets, sufficient time for biological evolution and an environment free of life-extinguishing supernovae. We identify the Galactic habitable zone (GHZ) as an annular region between 7 and 9 kiloparsecs from the Galactic center that widens with time and is composed of stars that formed between 8 and 4 billion years ago.

Cosmological magnetic fields vs. CMB – Tina Kahniashvili Tue. February 24th, 2004
11:30 am-12:30 pm

The cosmological perturbations induced by primordial magnetic fields and its influence on cosmic microwave background (CMB) radiation will be discussed. In particular, CMB temperature anisotropies, polarization, and temperature-polarization cross correlations, as well as Faraday rotation effect will be presented. The possible observational CMB tests to detect primordial magnetic fields will be discussed.

Looking for Dark Energy with the SDSS and WMAP – Ryan Scranton Tue. February 10th, 2004
11:30 am-12:30 pm

We present measurements of the angular cross-correlation between luminous red galaxies from the Sloan Digital Sky Survey and the cosmic microwave background temperature maps from the Wilkinson Microwave Anisotropy Probe. Looking at a number of redshift slices and CMB bands, we find a statistically significant achromatic positive correlation between these data sets, consistent with the expected signal from the late Integrated Sachs-Wolfe effect. We do not detect any anti-correlation on small angular scales as would be produced by a large Sunyaev-Zel’dovich effect, although we do see evidence for some SZ effect in our highest redshift samples. Assuming the flat universe found by the WMAP survey,

The Pierre Auger Observatory: A New Era Dawning in for Cosmic Rays – Corbin Covault Tue. February 3rd, 2004
11:30 am-12:30 pm

We are apparently at a unique moment in the history of cosmic ray physics. The origin of Ultra-High Energy Cosmic Rays (UCECR) has persisted as a profound astrophysical mystery for decades. But recently, the two premiere experiments for the detection of UHECR (AGASA and HiRes Fly’s Eye) have reported their best results — the culmination of many years of observations and analysis. These results might have been expected to provide key insight into to a new determination of the origin of cosmic rays, except for one fact: the two experiments, AGASA and HiRes have presented results that apparently contradict each other in several ways.

Cosmological Observatiions of the QCD and Electroweak Early Universe Phase Transitions – Leonard Kisslinger Tue. January 27th, 2004
11:30 am-12:30 pm

Transitions

My coworkers and I have shown that if the QCD phase transition, at about T=150 MeV, is first order, the bubble nucleation and collisions would produce magnetic effects, which would give polarization correlations of the Cosmic Microwave Background Radiation distinct from those predicted by other theoretical cosmological studies. The Electroweak phase transition at T=Higgs Mass is first order in the minimal supersymmetric model, with the mass of the stop (partner of the top quark) being of the order of the Higgs. Applying this theory we are studying magnetic fields generated during the EW phase transition as seeds for galactic magnetic fields.

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