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Past Events

Event Date Summary
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.


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