College of Arts and Sciences

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.

Continue reading… Boundary Localized Symmetry Breaking and Topological Defects – Matthew Martin

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.

Continue reading… The Ages of the Oldest Stars – Brian Chaboyer

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.

Continue reading… Gravity and Horizon Entropy – Ted Jacobson

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,

Continue reading… Technique for WIMP dark matter detection using pulse-shape discrimination in noble liquids – Mark Boulay

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.

Continue reading… Indirect signals from Dark Matter – Francesc Ferrer

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”

Continue reading… A Geometric approach to Distinguish Between a New Source and Random Fluctuations: Applications to High-Energy Physics – Ramani S. Pilla

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.

Continue reading… Ultra-high energy neutrinos – Mike Duvernois

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.

Continue reading… CMB/LSS correlation as a probe of dark energy – Levon Pogosian

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.

Continue reading… Brane cosmology with an anisotropic bulk – Dani Steer

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,

Continue reading… The future of dark energy measurements – Dragan Huterer

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.

Continue reading… Theoretical Constraints on the Dark Energy Equation of State – Mark Trodden

TBA

Continue reading… Observing the Cosmic Infrared Background with Frequency Selective Bolometers – Thushara Perera

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.

Continue reading… Bayesian Analysis of the WMAP Data – Ben Wandelt

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.

Continue reading… Inflation, strings and the CMB – Ana Achucarro

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.

Continue reading… Possible evidence for spatial fluctuations in dark energy – Christopher Gordon

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.

Continue reading… Confronting Inflation with Observation – William Kinney

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.

Continue reading… Physics of the black hole-brane interaction – Dejan Stojkovic

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.

Continue reading… Racetrack Inflation – Jose Blanco-Pillado

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.

Continue reading… First Results from the CAPMAP Experiment – Phil Farese

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.

Continue reading… Affleck-Dine Leptogenesis Induced by the Flaton of Thermal Inflation – Wan-il Park

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.

Continue reading… Results from the Sudbury Neutrino Observatory Salt Phase and the Future of the SNO Detector – Darren Grant

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.

Continue reading… BPS bounds of F- versus D-term strings and their cosmological implications – Filipe Freire