7 January 2005	4 February 2005	11 March 2005
14 January 2005	18 February 2005	18 March 2005
21 January 2005	25 February 2005
28 January 2005	4 March 2005

Brian Odom, Kavli Institute for Cosmological Physics

A search for physics beyond the Standard Model: measurements of the fine structure constant  

I will give an overview of recent measurements of the fine structure constant and of its possible time dependence. The significance of these measurements in terms of searches for physics beyond the standard model will be discussed. I will also present preliminary results for the newest and most precise measurement of the fine structure constant, based on the first fully quantum measurement of the electron magnetic moment, performed at Harvard University.

Tarek Saab

From milliKelvin to MegaKelvin: How superconductivity can help elucidate cosmology  

Recent great steps taken in the fields of cosmology and astrophysics have lead, inevitably, to new and more detailed sets of questions. X-rays hold the clue to some of the answers by providing diagnostics of the hot inter-stellar gases and plasmas where temperatures reach MegaKelvin (or keV). Superconductors enter the picture by making it possible to satisfy the desire for large, high quality data. In the last few years, detectors based on superconducting technology, have reached maturity and are finding applications in various areas of astrophysics ranging from x-ray spectroscopy to Dark Matter detection. In addition, new concepts based on other low temperature phenomena are being developed and targeted at future experiments. This talk will describe how astrophysics’ desire for higher count rates, energy, timing, and position resolution can be satisfied with detectors operating at mK temperatures.

Lifan Wang, LBL

Supernova Studies and Supernova Cosmology  

In recent years, Type Ia supernovae (SNIa) have emerged as the most precise cosmological distance indicators. I will discuss recent observational progresses on the studies of the nature of SNIa, based largely on a multi-year effort of spectropolarimetry observations collected at the ESO-VLT. These observations reveal that SNIa ejecta are highly aspherical at the highest velocity, whereas the asphericity decreases at layer with decreasing expansion velocities. There are indications that the asphericity is dominated by chemical inhomogeneities of the size of the photosphere at the time of optical maximum (~11,000 km/sec). There are strong evidences of the existence of detached clumpy layers, likely enriched in calccium, moving at the highest velocities (~22,000 km/sec) in some SN Ia ejecta. These new findings are not expected in popular models of SN Ia explosions. They provide important clues to the physics of SN Ia explosions. For cosmological applications, I will present recent results using the Color-MAGnitude Intercept Calibration (CMAGIC) of SN Ia. I will discuss future projects of SN Ia observations that aim to obtain a significant sample of SNIa with spectropolarimetry data. I will also discuss the prospects of routine discovery of gravitationally lensed SNIa, and the use of them as cosmological probes.

Hiranya Peiris, Kavli Institute for Cosmological Physics

Observing Trans-Planckian Signatures in the Cosmic Microwave Background  

I will examine the constraints cosmological observations can place on any trans-Planckian corrections to the primordial spectrum of perturbations underlying the anisotropies in the Cosmic Microwave Background. Using a specific "toy model", I will present a case study for the sort of constraints one could hope to apply on a well-motivated model of trans-Planckian physics from future high-precision CMB data. Our results show that the amplitude of the tensor perturbations is directly correlated with the detectability of any trans-Planckian modulation in the primordial power spectrum. This is likely to be true for any trans-Planckian modulation in the paradigm of slow-roll inflation.

Hsiao-Wen Chen, MIT

Unmasking Damped Lya Absorbing Galaxies  

I will present current results from searching for galaxies giving rise to damped DLA absorbers (DLAs) at z<1. Using 14 galaxies that are known to produce DLA features in the spectra of background QSOs, I will show that intermediate-redshift galaxies possess large HI envelope out to 24-30 h^{-1} kpc radius. In addition, the photometric and spectral properties of these galaxies confirm that DLA galaxies are drawn from the typical field population, and not from a separate population of low surface brightness or dwarf galaxies. Comparisons of the ISM abundances of the DLA galaxies and the metallicities of the absorbers at large galactic radii suggest that some DLAs originate in the relatively unevolved outskirts of galactic disks. An abundance profile characterized by a radial gradient of -0.041+/-0.012 dex per kiloparsec (or equivalently a scale length of 10.6 h^{-1} kpc) is found from galactic center to 30 h^{-1} kpc radius based on an ensemble of six galaxy-DLA pairs. Finally adopting this abundance gradient and known N(HI) profiles of nearby galaxies, I will show that the on-average low metal content of the DLA population can arise naturally as a combination of gas cross-section selection and metallicity gradients commonly observed in local disk galaxies.

Yong-Seon Song, KICP

Looking for an extra dimension with two windows on acceleration and gravitation  

The cosmic acceleration was discovered in one of the brane-based models as well as dark energy model. Growth factors are different in the two models when one adjusts parameters to get nearly identical H(z). The two models could be distinguished with independent determinations of both geometrical factors and the growth factors. Cosmic shear due to gravitational lensing, can be used to simultaneously determine the distance-redshift relation, D(z), and the rate of growth of density contrasts, g(z). Both of these functions are sensitive probes of the acceleration. Their simultaneous determination allows for a consistency test and provides sensitivity to physics beyond the standard dark energy paradigm.

Tanmay Vachaspati, Case Western University

Islands in the Lambda-sea  

We propose an alternate cosmological model in which our observable universe is an island in a cosmological constant sea. Initially the universe is filled with cosmological constant of the currently observed value but is otherwise empty. In this eternal or semi-eternal de Sitter spacetime, we show that local quantum fluctuations (upheavals) can violate the null energy condition and create islands of matter. The perturbation spectra of quantum fields other than that responsible for the upheaval, are shown to be scale invariant. With further cosmic evolution the island disappears and the local universe returns to its initial cosmological constant dominated state.

Artuu Rajantie

Cosmic strings and high energy physics  

I will discuss the formation of topological defects such as cosmic strings in the early universe. Depending on physics at very high energies, defects may be formed by different mechanisms. I will review these mechanism, and show that they have certain distinct consequences in the properties and distribution of the produced defects. Astronomical observation of cosmic strings would therefore give us direct information about very high energy physics.

Bill Jones

Measurements of the Temperature and Polarization anistropies with Boomerang  

Arthur Lue, Case Western University

Braneworlds and Beyond: Differentiating Modified Gravity from Dark Energy  

The nature of the fuel that drives today's cosmic acceleration is an open and tantalizing mystery. I entertain the suggestion that the acceleration is not the manifestation of yet another new ingredient in the cosmic gas tank, but rather our first real lack of understanding of gravitational physics. I discuss first an intriguing braneworld model (Dvali-Gabadadze-Porrati) and extend the discussion to a more general context, addressing questions about modified-gravity cosmologies and dark energy at astrophysically interesting, and even solar sytem, scales, with these distinctions being subject to imminent observational discrimination.

26 January 2005	23 February 2005
9 February 2005	9 March 2005

Alex Szalay, John Hopkins University

Cosmology with Large Datasets  

George Dvali, New York University

Gravity at largest observable distances  

Rachel Somerville

On the Origin of the Red Sequence and Bimodality of Galaxy Properties  

The color-magnitude relation and the related dichotomy in the morphological, structural, and spectro-photometric properties of galaxies are well-known and fundamental observed properties of galaxies. These relations seem to be largely in place as early as redshift one. However, standard models of galaxy formation set within the Cold Dark Matter paradigm fail to reproduce either the color-magnitude relation or the observed strong bimodality in galaxy properties. I will show that including the feedback from Active Galactic Nuclei in such models may hold the key to understanding these fundamental observations.

Licia Verde, University of Pennsylvania

constraints on the redshift dependence of the dark energy potential  

Cosmology has now a standard model. This model is described by a handful of cosmological parameters, now determined with unprecedented precision, many of them are measured in multiple independent ways. The standard cosmological model is simple, yet puzzling. The big challenge is to shed some light on the dark energy component, which reveals itself only through the acceleration of the universe. Under the assumtion that dark energy is a slowly rolling scalar field, We develop a formalism to characterize the redshift evolution of the dark energy potential. We show that in principle the shape of this potential can be recovered non-parametrically. Since presently available data do not allow a non-parametric reconstruction, we consider a generic parametric description and use observations of passively evolving galaxies derive constraints on the shape of the dark energy potential in the range 0.1

2 March 2005

16 March 2005

Don Backer, University of California, Berkeley

Pulsar Timing Array: Probing the Nanohertz Gravitational Wave Background  

Sarah Gallagher, University of California, Los Angeles

New Insights into Quasar Wind Structure  

17 February 2005

Jacob Bourjaily, University of Michigan

What is the Cosmological Significance of a Discovery of Wimps at Colliders or in Direct Experiments?  

Although a discovery of wimps either at colliders or in direct 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, even allowing all needed assumptions about cosmology and astrophysics. However, it may be possible to determine the density of wimps by combining data from both experiments. I present a general method to do this in the case of supersymmetric dark matter, and describe how similar studies could be made for other wimp candidates.

10 February 2005

28 February 2005

10 March 2005

Karl Van Bibber, Lawrence Livermore National Laboratory

A Large-Scale Search for Dark-Matter Axions  

Recent progress in experimental cosmology has provided a reasonably precise understanding of the overall energy density budget of the Universe. Matter accounts for about a quarter, only a small fractionof which can be baryonic. What constitutes the predominant dark matter is unknown, although particle relics from the Big Bang are implied, a sufficiently light axion being a leading candidate. Halo axions may be detected by their coherent conversion to microwave photons in a high-Q cavity permeated by a strong magnetic field. A collaboration from LLNL, Florida and Berkeley has developed the world's quietest radio receiver for this search and has achieved sensitivity well into the range of axion models. The experiment is now being upgraded with near-quantum-limited SQUID amplifiers, a breakthrough technology which will reduce the noise temperature of the experiment by a factor of 30, thus enabling a truly definitive search.

Roger Penrose, Oxford University

The Road to Reality  

Oxford University Professor Roger Penrose will discuss his new book, “The Road to Reality” In his remarkable, readable, and massive new book, (over 1100 pages) physicist and mathematician Roger Penrose offers readers the most comprehensive and sophisticated account yet of the physical Universe and the essentials of its underlying mathematical description. Penrose neither simplifies the science nor dodges the difficult questions, but instead tackles all the issues and controversies, including: the role of numbers in physics, ideas of calculus and modern geometry, visions of infinity, the Big Bang, black holes, the profound challenge of the second law of thermodynamics, String Theory and more. The exposition also highlights the awesome beauty of contemporary Physics and Mathematics.

Raul Jimenez, University of Pennsylvania

Watching galaxies assemble: cosmological star formation and mass assembly history form SDSS spectra