1 January 2004	30 January 2004	27 February 2004
9 January 2004	6 February 2004	12 March 2004
16 January 2004	13 February 2004
23 January 2004	20 February 2004

Licia Verde, University of Pennsylvania

TBA  

Dragan Huterer, Case Western Reserve University

Multipole Vectors and the CMB Sky  [Online talk]

I will present "multipole vectors", a new basis to represent the CMB anisotropy. In this representation, each multipole order l is represented by l unit vectors pointing in directions on the sky and an overall magnitude. Like the usual spherical harmonics, multipole vectors form an irreducible representation of the proper rotation group SO(3) however, they are related to the familiar spherical harmonic coefficients, alm, in a highly nonlinear way. I will present evidence that oriented areas of planes defined by these vectors, between multipole pairs with 2 <= l <= 8 and computed from WMAP maps, are inconsistent with the isotropic gaussian hypothesis at about 99% confidence. I will discuss these results, and future work and possible applications of the multipole vectors.

Benjamin McCall

The Chemistry of H3+ in the Diffuse Interstellar Medium  

H3+, the simplest polyatomic molecule, plays a key role in dense interstellar clouds as the initiator of ion-molecule chemistry. The detection of H3+ in diffuse interstellar clouds came as a surprise, however, and suggested a serious (factor of ~100) problem in the simple model of diffuse cloud chemistry. In particular, this observation raised questions as to the applicability of laboratory measurements of the H3+ dissociative recombination rate to interstellar conditions. We have recently measured the dissociative recombination rate of rotationally cold H3+ ions in an ion storage ring, and have also detected H3+ in the classical diffuse cloud towards ? Persei, where the electron fraction is known from previous observations. This combination of new laboratory measurements and astronomical observations has eliminated two of the primary uncertainties in the chemical model, and implies a previously unrecognized and significant enhancement in the cosmic-ray ionization rate in the diffuse interstellar medium.

Constance Rockosi, University of Washington

Galaxy Assembly in the Present Day  

New detections of coherent streams and merger remnants in the Galaxy have reinforced our picture of the Galaxy under construction even at the present day. This continuous process of gravitational interaction and accretion leaves its signature on the global density and kinematic structure of the Galaxy, allowing us to unravel the recent merger history of the Milky Way. With the right instrumentation, we can apply this close-up view of galaxy interactions to the interpretation of the kinematics, population content, stellar and dark matter density profiles of nearby galaxies and groups, shedding important light on the processes which set the distribution of galaxy properties we observe today and in the earlier universe.

Christopher Gordon, Center for Cosmological Physics

Observational Constraints on Neutrino Isocurvature Modes from the Curvaton Model of Inflation  

In the curvaton model of inflation, where a second scalar field, the "curvaton", is responsible for the observed inhomogeneity, a non-zero neutrino degeneracy parameter may lead to a characteristic pattern of isocurvature perturbations in the neutrino, cold dark matter and baryon components. Where the neutrino degeneracy parameter is the neutrino chemical potential divided by the neutrino temperature and isocurvature perturbations are perturbations in the particle number ratio of different particle species. We find the current data (WMAP, 2dF, HST) can only place upper limits on the level of isocurvature perturbations. These can be translated into upper limits on the neutrino degeneracy parameter. In the case that lepton number is created before curvaton decay, we find that the limit on the neutrino degeneracy parameter is comparable with that obtained from Big-bang nucleosynthesis. For the case that lepton number is created by curvaton decay we find that the absolute value of the non-Gaussianity parameter,fnl, must be less than 10 (95% confidence interval).

Stelios Kazantzidis, University of Zurich

Structural Evolution of Cold Dark Matter Substructure and the Missing Satellites Problem  [Online talk]

Hierarchical Cold Dark Matter (CDM) models constitute the prevailing paradigm for interpreting the formation and evolution of structure in the universe. A generic prediction of these models is that massive dark matter halos are assembled by numerous merger events, leaving many tightly bound entities known as substructure. I present results on the structural evolution of these low-mass dark matter substructures combining ``low-resolution'' satellites from cosmological N-body simulations of parent halos with N=10^7 particles with high-resolution individual subhalos orbiting within a static host potential. In contrast to earlier investigations indicating that the central density cusp of CDM subhalos becomes shallower as a result of tidal interactions, I find that their inner density slope is unaffected even after several pericentric passages. I discuss the implications of these results for vital issues including the recent attempts to alleviate the missing Galactic satellites problem by means of allowing the observed dwarf spheroidal satellites to be embedded within dark halos with maximum circular velocities as large as 60 km/s.

Risa Wechsler, Center for Cosmological Physics

Modeling SDSS Clusters: Galaxies, Masses, and Cosmology  

The Sloan Digital Sky Survey, which is still in progress, has already identified the largest sample of galaxy clusters in the Universe. The abundance of massive clusters is a powerful discriminator between cosmological, but its promise can only be realized by using a large cluster sample with observable properties that can be closely connected to halo mass. Advances in cluster finding techniques, combined with large mock galaxy catalogs that match the relation between galaxy luminosity,color, and environment, now make this possible with optical data. We show how these mock catalogs can be used to calibrate cluster finding techniques and make direct predictions in observational space -- and how a combination of mass measurements and clustering statistics can be used to constrain the cluster mass scale and put constraints both on cosmology and on the relation between galaxies and dark matter halos.

P.K. Kabir, The University of Virginia

Matter-Imbalance in the Universe  

Craig Hogan, University of Washington

Discrete Spectrum of Inflationary Perturbations  

Several arguments suggest that quantum-gravity effects may not only slightly alter the slope of inflationary perturbations, but may also lead to a discrete spectrum, instead of the continuous one predicted by the standard calculation using field theory on a quasi-classical spacetime background. This effect will be discussed from the point of view of the foundations of field theory, by adding simple self-gravity operators to the field Hamiltonian, and from the point of view of the holographic principle. Possible observational effects of a discrete spectrum will be briefly discussed.

Francisco Prada, ING

Dark matter in Galaxies: Satellites and Neutralinos  

Velocities of satellites of galaxies together with weak lensing provide the best way to probe the mass distribution of individual field galaxies at large radii. Using the Sloan Digital Sky Survey we find that the velocity dispersion of satellites declines with distance to the host galaxy. This decline agrees remarkably well with the distribution of dark matter predicted by the cosmological models in the peripheral parts of galaxies. A relation between the satellite velocity dispersion with the host luminosity as well as an estimation of the host mass-to-light is given. We use numerical simulations to test prescriptions for correcting the effects of interlopers who play an important role in the analysis. I will discuss our recent results. If dark matter is made of supersymmetric particles, the center of galaxies should emit gamma-rays produced by their self-annihilation. I will present accurate estimates of continuum gamma-ray fluxes due to neutralino annihilation in the central regions of the Milky Way. We use detailed models of our Galaxy, which satisfy available observational data, and include some important physical processes, which were previously neglected. In the next 1-2 years there is a hope that the new generation of Imaging Atmospheric Cherenkov Telescopes would detect the gamma-ray signal coming from the annihilation products of the SUSY dark matter in galaxy halos.

21 January 2004	18 February 2004	17 March 2004
4 February 2004	3 March 2004

Jonas Zmuidzinas, Caltech

Superconducting Detectors for Cosmology and Astrophysics  

Progress in astrophysics and cosmology is closely tied to the sensitivity of telescopes and instruments. A recent example is provided by the measurements of the CMB anisotropy made by experiments such as Boomerang, DASI, and now WMAP, which were enabled by progress in the underlying HEMT amplifier and bolometer detector technologies. In the future, the measurement of the polarization of the CMB may provide information about the inflationary epoch in the very early universe. To achieve this, it will be necessary to improve CMB instrument sensitivities by several orders of magnitude. I will describe a variety of ways in which the interesting and unusual properties of superconductors are being exploited in order to deliver the required advances in sensitivity. In addition, I will also highlight other astrophysical applications of superconducting detectors, particularly at long wavelengths.

Max Tegmark, U Penn

Cosmology with the SDSS and WMAP  

I present the most accurate galaxy clustering measurements to date from the SDSS and discuss what we do and don't know about inflation, dark energy, dark matter and neutrinos from this, WMAP, gravitational lensing, the Lyman alpha forest and other cosmological probes. I outline my view of the most exciting challenges ahead.

Sunil Golwala, Caltech

Observing the Sunyaev-Zeldovich Sky (and the Atmosphere) with Bolocam  

Blind surveys for galaxy clusters using the Sunyaev-Zeldovich effect are becoming one of the new frontiers in cosmology, promising to tell us about both about global cosmological parameters as well as cluster formation and astrophysics. We have recently conducted such a survey at 150 GHz using Bolocam, a 144-element mm-wave bolometer camera, on the Caltech Submillimeter Observatory. We describe the instrument and report on the state of analysis of this data set. We describe in detail how we are attacking the problem of sky noise,which will be a common challenge for upcoming ground-based SZ instruments at 150 GHz such as APEX, ACT, and SPT. We also present highlights of data sets taken at 1.1 mm to search for dust-obscured ultraluminous galaxies and cold protostellar condensations in our own galaxy.

Martin Einhorn, University of Michigan

The Black Hole Information Paradox, Entropy & Entanglement  

Hawking discovered that black holes not only have entropy but radiate with a thermal spectrum. What happens to information that passes inside? Is it encoded in the radiation? Does it disappear forever? Does it remain embodied in a remnant? Does black hole evaporation require a modification of quantum mechanics itself? Does theBeckenstein-Hawking entropy law require fewer dynamical degrees of freedom. Does it imply nonlocal dynamics, a breakdown of local quantum field theory? Does string theory come to the rescue? Does spacetime with a cosmological constant have intrinsic entropy? Challenging some of our most dearly held beliefs, no definitive theoretical answers yet exist.

Glennys Farrar, New York University

Unconventional Dark Matter Scenarios  

The dark sector is commonly assumed to be very boring, consisting of almost non-interacting cold dark matter. However reality may be much richer and more interesting, and CDM may be just an effective description, suitable for summarizing cosmological evolution. The following questions motivate considering alternatives to LCDM: > Why is the density of ordinary matter comparable to that of dark matter, when -- in the conventional picture -- their abundances are governed by entirely different physics? > Does the dark sector play a part in accounting for the baryon asymmetry in the visible sector? > Particle masses in the visible sector are governed by the Higgs mechanism -- could the Dark Energy be due in part to a Higgs-like particle for the dark matter? > Why should the dark sector be almost trivial when the visible sector is so complex? (With only gravity as a probe so far, are we simply missing the complexity?) I will discuss possible answers to the above questions, with an emphasis on observational approaches to studying the properties of the dark sector in greater detail.

22 January 2004

11 March 2004

Greg Rudnick

The Cosmically Averaged Universe out to z~3  

Deep Near Infrared Observations are key in obtaining a comprehensive view of the high redshift Universe, in comparing observations at high-z directly to those in the local Universe, and in accessing the stellar populations which contribute significantly to the stellar mass of galaxiues. In addition, by averaging all of the light in galaxies together, robust determinations of the cosmic color and stellar mass-to-light ratio can be determined, even in the face of bursty star formation histories (SFHs) and using small pencil beam surveys. I present results from the Faint Infrared Extragalactic Survey (FIRES) and quantify the evolution in the integrated galaxy population over 0

Marvin Weinstein, Stanford University

Quantized Cosmology  

I discuss the problem of inflation in the context of Friedmann-Robertson-Walker cosmology and quantize it in a way which parallels the classical discussion. Two of the Einstein equations arise as Heisenberg equations of motion, but the Friedmann equation, which classically is a constraint which defines physical solutions, acquires a welcome quantum correction. The general formalism is clarified by application to the case of de Sitter space, where I show that the welcome additional terms in the quantum version of the Friedmann equation eliminate the problem of the big crunch. I finally discuss the possible existence of measurable corrections to the anisotropy in the CMB radiation due to these quantum effects.

9 February 2004

Alexey Finoguenov, MPE, Munich

XMM-Newton surveys of structure and scaling of IGM of groups and clusters of galaxies  

XMM-Newton observations of two-dimensional distribution of gas properties in clusters of galaxies reveal a significant amount of substructure. We identify the entropy to be most sensitive to both late stage of merger with the associated slow buoyancy action on relaxation of the cluster and on the scale of strong shocks, which change the entropy. The pressure maps are much more regular and thus could be used to infer the the dark matter distribution. Putting groups and clusters of galaxies on scaling relations for entropy and pressure, we identify high scatter amoung the groups as well as presence of the low entropy gas at outskirts of clusters as most challenging issues for using these systems as simple cosmology probes.