Talks & Events
KICP Colloquia: 2004
Superconducting Detectors for Cosmology and Astrophysics
Jonas Zmuidzinas, Caltech
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.
Cosmology with the SDSS and WMAP
Max Tegmark, U Penn
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.
Observing the Sunyaev-Zeldovich Sky (and the Atmosphere) with Bolocam
Sunil Golwala, Caltech
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.
The Black Hole Information Paradox, Entropy & Entanglement
Martin Einhorn, University of Michigan
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.
Unconventional Dark Matter Scenarios
Glennys Farrar, New York University
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.
Gamma-Rays, Cosmic Backgrounds and the Universe, as Calorimeter
Scott Wakely, University of Chicago
Over long distances, the Universe is largely opaque to very high energy (VHE) radiation. I'll talk about the implications of this for GeV/TeV gamma-ray measurements, and discuss some possible methods for inferring interesting cosmological information about the production and composition of extragalactic background radiation fields at different wavelengths.
Two Tests of Environmental Affects on Galaxy Formation
Ravi Sheth, University of Pittsburgh
Galaxy formation models make specific predictions for how the properties of galaxies depend on enviroment. I will outline the physical assumptions on which these predictions are based, and will then describe some tests of these assumptions which can be made with galaxy surveys which are just becoming available.
21 cm fluctuations: a new window for cosmology
I will discuss what 21 cm fluctuations produced by gas at high redshift can teach us about cosmology. I will discuss some of the challenges in making these observations.
Eternal Inflation, Multiple Universes, and other Dark Matters
Anthony Aguirre, Institute for Advanced Study School of Natural Science
Several ideas in cosmology, including inflation, string cosmology, and quantum cosmology, have led to the notion of multiple "universes" with different properties. This immediately raises the question of which (theoretical) universe we should compare to ours, and also provides a context for application of the "anthropic principle". I will outline some of the issues and problems that arise in multiverse theories, and describe some specific progress that has been made toward resolving (or making more acute) these problems.
Martin White, UC, Berkeley
The study of modern cosmology has been tremendously advanced by probes for which detailed comparison between theory and observation is possible. However, our supply of clean cosmological probes is limited. Weak gravitational lensing is one such probe, combining theoretical control and experimental tractability with sensitivity to interesting cosmological parameters. In this talk I will review the current state of the art in weak lensing theory and experiment, and discuss several areas of current research interest.
Detecting and Studying the Sources which ended the Dark Ages
Richard Ellis, Caltech
The final frontier in understanding the origin of stellar systems lies beyond a redshift of 5. Sources of ultraviolet radiation during this period of cosmic history may have played a key role in ending the "dark ages" when the bulk of hydrogen was neutral. The dominant radiating sources in this era will doubtless be faint and probably of low mass making their detection a considerable challenge. I will discuss various ways of making progress in this area with current facilities, prior to the completion of new facilities such as the James Webb Space Telescope and the Thirty Meter ground-based telescope.
Observational cosmology as a probe of fundamental physics
Uros Seljak, Princeton University
I will review recent results from Sloan Digital Sky Survey (SDSS) on galaxy clustering, weak lensing and Ly-alpha forest. In combination with WMAP results on cosmic microwave background these tracers of large scale structure give us an unprecedented view of the universe over a broad range of scales and epochs. I will describe how we can test fundamental theories of the universe with these observations, focusing on three questions: do neutrinos have mass? what provided initial seeds of structure in the universe? what is the nature of the dark energy? Existing data and corresponding analyses already greatly improve the precision of these tests, which will be improved further in the future. The progress in observations requires a parallel progress in our theoretical understanding of astrophysical processes such as physics of galaxy formation and physics of inter-galactic medium. I will describe recent developments in these areas.
First Large-Scale Structure Results from the DEEP2 GalaxyRedshift Survey: Galaxy Clustering, Environment, Groups and Voids at z=1
Allison Coil, UC Berkeley
I will discuss the first large-scale structure results from the z=1 DEEP2 Galaxy Redshift Survey. We study both galaxy clustering and environment as a function of color, spectral type, and luminosity and find that red, absorption-dominated, passively-evolving galaxies are more strongly clustered than blue, emission-line, actively star-forming galaxies. The implied galaxy bias in our sample is b~1.0-1.2. I will show initial results on the relationship between galaxy properties and environment in the DEEP2 sample and compare our results to similar studies recently completed in the SDSS. Finally, I will present our first group catalog and our measured void probability distribution function and discuss their implications.
Inside Black Holes
Andrew Hamilton, University of Colorado, Boulder
What really happens inside black holes? If you fell into one, what would you see, what would you experience? It is well known that, except for the single case of the Schwarzschild solution, the vacuum solutions for the interiors of black holes are inconsistent as endpoints of gravitational collapse, because the cores of vacuum black holes are gravitationally repulsive. Instead, black holes must contain matter. In this talk I consider self-similar solutions for charged spherical black holes, taking charge as a surrogate for angular momentum. The black holes are allowed to accrete a mix of baryons and non-baryonic Dark Matter. I show how details such as the electrical conductivity, and the cross-section for interaction between baryons and Dark Matter, play crucial roles in determining the internal structure of a black hole, which proves to be surprisingly complex. Real time visualizations of such black holes will be shown.