10 January 2003	7 February 2003	14 March 2003
17 January 2003	21 February 2003	21 March 2003
24 January 2003	28 February 2003
31 January 2003	7 March 2003

Tokonatsu Yamamoto, CfCP

Anisotropy of Highest Energy Cosmic Ray and propagation of Ultra-High Energy Nucleus  [Online talk]

Recently, small scale anisotropy in the distribution of arrival direction of Ultra High Energy Cosmic Ray (UHECR)has been detected by AGASA. They reported clusters above 10^19 eV correlated with the Galactic magnetic field. This result is an indication that UHECRs come from extra-galactic point sources and are charged particle. Motivated by this observational result, we have simulated propagation of high energy nucleus in the extra-galactic photon and magnetic field. Based on the result of this simulation, energy distribution of the UHECR will be discussed.

Michael Santos, Caltech

Galaxy Formation: The Reionization Years  

The reionization of hydrogen represents not only a landmark achievement by early luminous sources, but also had a considerable effect on the subsequent formation of stars and galaxies: reionization inhibits star formation in some proto-galaxies, in a way that depends on their total mass and formation history. I will show results suggesting that reionization plays a crucial role in understanding globular cluster formation. I will also present observations of z=5 galaxies, where the Lyman-alpha line luminosity function provides a test of the effect of reionization on star formation in proto-galaxies.

Maximo Ave, CfCP

Mass composition of high energy cosmic rays  

Efforts to understand the origin of cosmic rays at any energy are greatly hampered by our lack of knowledge of the mass distribution in the incoming cosmic ray beam. Even with the traditional ground arrays it has been possible to devise ways of deducing the primary energy that are reasonably independent of model and mass uncertainties, at least at the 30 \% level. However use of the data on the energy spectrum and arrival direction distribution to decide between various origin models does require knowledge of the primary mass distribution. We try to review the experimental status of mass composition measurements of primary cosmic rays above 1019 eV.

Mark Hoffman

Can w be less than -1?  

Models of dark energy are conveniently characterized by the equation-of-state parameter w=p/ ho, where ho is the energy density and p is the pressure. Imposing the Dominant Energy Condition, which guarantees stability of the theory, implies that wgeq -1. Nevertheless, it is conceivable that a well-defined model could (perhaps temporarily) have w<-1 , and indeed such models have been proposed. We study the stability of dynamical models exhibiting w<-1 by virtue of a negative kinetic term. Although naively unstable, we explore the possibility that these models might be phenomenologically viable if thought of as effective field theories valid only up to a certain momentum cutoff. Under our most optimistic assumptions, we argue that the instability time scale can be more than the age of the universe, but only if the cutoff is at or below 100 MeV. We conclude that it is difficult, although not necessarily impossible, to construct viable models of dark energy with w<-1 observers should keep an open mind, but the burden is on theorists to demonstrate that any proposed new models are not ruled out by rapid vacuum decay.

Thushara Perera, CfCP

Transition Edge Sensors in bolometers and particle detectors  [Online talk]

Due to a variety of advantages they offer, Transiton Edge Sensors,(TESs)are slated for use in many upcoming experiments in astrophysics. I will describe the principles of operation and biasing and readout scheme used with TESs which involves the use of SQUID magnetometers. I will also discuss why they are desirable for use in bolometers and dark matter detectors. The desireable properties include superior speed, linear and stable response, low noise levels, and adaptability to a multiplexed readout scheme which facilitates their use in large-scale arrays.

Erin Scott Sheldon, CfCP

"Constraints on Galaxy Biasing from Weak Lensing in the Sloan Digital Sky Survey"  [Online talk]

I will present a galaxy-galaxy lensing study based upon data from the Sloan Digital Sky Survey. Galaxy-galaxy lensing on intermediate to large scales(R>200kpc) is a direct measure of the galaxy -mass cross correlation function w_{gm}. By comparing w_{gm} bias between the galaxy distribution and the underlying mass distribution. This relatiopnship is of fundamental importance to the understanding of galaxy formation. Because lensing is a measure of the excess mass, these measurements can also be used to constrain the mass-to-light ratio of the large scale structure surrounding galaxies. By comparing to the galaxy-luminosity correlation function w_{gL}, we constrain the bias between luminosity and mass, and the radial dependence of the mass-to-light ratio around galaxiies.

Andrew Sonnenschein

Searching for dark matter with superheated liquids  

The identification of the non-baryonic component of the dark matter is one of the most urgent problems in cosmology. This is a very exciting problem for experimentalists, because of the possibilities for greatly increased sensitivity that are being opened up by new detection technologies. Weakly interacting massive particles (WIMPs), especially the neutralinos predicted by supersymmetry, are a leading candidate to be the dark matter, and the search for these particles is now being intensely pursued by diverse methods, in experiments such as CDMs, DAMA, and ZEPPLIN. A particularly interesting detection technique for future experiments involves the use of bubble nucleation in superheated liquids to discriminate against backgrounds from environmental radioactivity. These experiments operate in a mode similar to bubble chambers, but under pressure conditions that reduce sensitivity to backgrounds. In principle, this approach can be used to construct very large detectors, which would improve sensitivity by orders of magnitude. I will discuss the initial attempts to use this effect in ongoing experiments, and a new variation on the technique which we are exploring at the Center for Cosmological Physics.

Alan Peel, University of California, Davis

Galaxy Cluster Peculiar Velocities and Cosmology  [Online talk]

Galaxy clusters are the next best thing for precision cosmology probes after the Cosmic Microwave Background. With the recent dramatic increase in sensitivity and resolution of sub-mm wavelength observations, we will soon begin to measure galaxy cluster peculiar velocities via the Sunyaev-Zel'dovich effect. However, detailed modeling of point sources, CMB comtamination and velocity/temperature substructure within the cluster itself is required to acquire useful measurements with sufficient precision for cosmology. I will discuss what cosmology can be accomplished with cluster velocities and seperately, how we an model observations to optimize velocity measurements. This is work in progress supported in part by a NASA Graduate Student Research fellowship.

Andreas Berlind, CfCP

Probing the Relation Between Galaxies and Dark Matter in the Sloan Digital Sky Survey  [Online talk]

The relation between the galaxy and mass distribution is uncertain because it depends on the complex and poorly understood process of galaxy formation. This "bias" between galaxies and mass has long been seen as an obstacle for studies of galaxy clustering tht attempt to constrain cosmological models. An alternative view, however, is that the existence of bias makes it possible to constrain galaxy formation theories by studying galaxy clustering. I will describe the "Halo Occupation Distribution", (HOD),a realtively new formulation of bias that is based on the distribution of galaxies in dark matter halos. I will illustrate the power of this approach and show how it can be used to measure the bias empirically and connect observations of galaxy clustering to the physics of galaxy formation. Finally, I will present constraints on the HOD from measurements of galaxy clustering in the Sloan Digital Sky Survey.

Daniel Holz, CfCP

Amplification from gravitational lensing:noise and science  

Because we live in an inhomogeneous universe, all distant sources are gravitationally lensed. We derive these lensing effects, paying particular attention to the distribution of amplifications of distant standard candles. Lensing is found to be an important source of noise in attempts to measure the evolution of the universe with high-redshift supernovae. We discuss various ways to minimize this lensing noise. As the lensing results from the gravitation of intervening matter, a direct measurement of the lensing signal shed light on the distribution of dark matter in the universe. We conclude with a discussion of the impact of lensing on proposed next generation high- redshift supernova surveys.

22 January 2003	26 February 2003	5 March 2003
19 February 2003	3 March 2003	19 March 2003

Mark Devlin, University of Pennsylvania

Millimeter Observations of the Early Universe from the High Atacama Plateau and the Not-So-High West Virginia Appalachians  

I will discuss the proposed Atacama Cosmology Telescope (ACT). ACT is a low background 6 meter diameter telescope designed to study the early universe with three large arrays of millimeter-wave detectors. I will also discuss the Penn Array Receiver (PAR). The PAR consists of a small 64 element array of TES detectors operating at 90 GHZ. It will be mounted on the 100 meter diameter Green Bank Telescope in West Virginia. Finally, I will give a brief status report on the Balloon-born Large Aperture Submillimeter Telescope (BLAST).

Sean Carroll, University of Chicago/CfCP

What General Relativity really means  [Online talk]

According to the cliche, you never understand a subject until you teach it. Not true it turns out to be necessary to write a textbook. I will give a pedagogical talk on aspects of GR which have become clear to me while writing such a book, focusing on: 1) the physical content of Einstein's equation, and 2) how GR could reasonably have been different, and consequently what alternatives are most worth of our attention. No prior knowledge of GR is assumed in fact it's discouraged.

Chung-Pei Ma, University of California, Berkeley

A Boltzmann Approach to Modern Cosmology  

I will describe a few examples of how the Boltzmann equation can help us understand the evolution of cosmic structures in the universe. One application is the gravitational clustering of massive neutrinos and the implications for the nature of ultra high energy cosmic rays. I will also discuss the surprising finding that cold dark matter collapses into a cuspy universal form and how a kinetic Boltzmann approach may shed light on the origin of this behavior.

Martin Einhorn, The University of Michigan

TBA  

Roberto Peccei

Is CP Violation universal, and what does it mean for the Universe?  [Online talk]

Neil J. Cornish, U Montana

LISA and the New Astronomy  

The Laser Interferometer Space Antenna (LISA) is one of the two Great Observatories to be built for NASA's Beyond Einstein program. Unlike the earlier Great Observatories, Hubble, Chandra, and Compton, LISA will be the first to explore the Universe from outside the electromagnetic spectrum. LISA will detect low frequency gravitational waves from a variety of sources, but LISA's primary mission is no more the detection of gravitons than Hubble's is the detection of photons. Rather, LISA will be a powerful astronomical observatory that will allow us to study how black holes form and how they evolve,perform a census of close binary systems in our galaxy and beyond, map the spacetime of a black hole, and place limits on the gravitational waves produced by the Bing Bang. The presentation will describe the LISA mission and explain how LISA can be used to do astronomy.

11 February 2003

Stephan Meyer, EFI/CfCP

Results From the First Year of the MAP Satellite Observations  

We report on the results of the first year of observation with the MAP satellite. The instrument has produced full sky maps at five frequencies from 20 to 100 GHz with the goal of measuring the Cosmic Microwave Background (CMB) anisotropy from 0.2 to 180 degrees. These maps and the CMB angular power spectrum derived from them are sensitive tests of models of the conditions and history of the early universe. Systematic effects in the measurements are small and well quantified owing to the design of the experiment. Galactic and extra-galactic foregrounds are characterized and separated from the CMB signal with high precision. The MAP data are combined with information from other cosmological probesto extend the range of models which are tested.