# BCG Seminars 2001-2002

May, 2002:

May 7, 12:30 pm
349 LeConte

May 14 , 12:30 pm
Maxim Perelstein
UCB
375 LeConte
Domain Walls as Dark Energy

April, 2002:

Apr. 16 , 12:00 noon
Cosmology Lunch
Probably LeConte 349 at noon

Bring your lunch and come ready to talk about cosmology. We will discuss astro-ph/0204043, Gravitational Lenses, the Distance Ladder and the Hubble Constant: A New Dark Matter Problem by C. Kochanek

Apr. 30 , 2:10 pm ( Note special time!)
joint string/cosmology seminar
Nemanja Kaloper
Stanford University
375 LeConte
Signatures of Short Distance Physics in the Cosmic Microwave Background

March, 2002:

Mar. 5 , 12:30 pm
349 LeConte

Mar. 12 , 12:30 pm
Alexei Razoumov
University of California, San Diego
375 LeConte
Towards Realistic Radiative Transfer In Numerical Cosmology
Photons escaping early objects in the Universe played major role in subsequent structure formation on all scales from the typical size of voids to galaxies down to individual protostellar clouds. I will present an ongoing effort to include radiative transfer into cosmological simulations. Computational challenges come both from multidimensional physics of radiative transfer and the need to resolve a large range of scales. One of the projects completed so far was computing stellar reionization -- the process in which ionizing radiation builds up from smaller scales. Our calculations demonstrate that the process by which the ionized regions percolate the Universe is complex, and that the idea of voids being ionized before overdense regions is too simplistic. Another example is modeling statistical properties of high-column density Ly\alpha absorbers at observable redshifts. These and other radiative transfer projects at the Laboratory for Computational Astrophysics at UC San Diego will be presented.

Mar. 19, 2:00 pm
Ue-Li Pen
CITA
SZ effect

February, 2002:

Feb. 5 , 12:30 pm
Cosmology Lunch
At LBL INPA conference room (Bldg 50, Room 5026)

Bring your lunch and come ready to talk about cosmology. We will discuss in part the recent AAS meeting and Chicago (CfCP) Dark Energy Meeting, overviews by E. Linder (of some of the things he noted) are here.

Feb. 12 , 12:30 pm
349 LeConte

Feb. 19 , 12:30 pm
Josef Jochum
375 LeConte
CRESST Dark Matter Search at Gran Sasso

Abstract:
CRESST (Cryogenic Rare Event Search using Superconducting Thermometers) is using cryogenic calorimeters for the direct search for WIMP dark matter candidates. Data taken by CRESST with a cryogenic detector system based on 262 g sapphire crystals has been used to place limits on WIMP dark matter in the Galactic Halo. The experiment was especially sensitive for low-mass WIMPs with spin-dependent cross sections and improves on existing limits in this region. Another type of detectors, using CaWO4 crystals, simultaneously measures scintillation light and phonons. By comparing the light and the phonon signal, electron recoils can be distinguished from nuclear recoils. This way the majority of background can be discriminated and the sensitivity for low WIMP counting rates can be increased by orders of magnitude. In 2001, CRESST had to move the entire set-up within the Gran Sasso laboratory. The CRESST data, the status of the move, of the detector development and the plans for upgrading CRESST will be presented.

Feb. 26 , 12:30 pm
Manoj Kaplinghat
University of California, Davis
375 LeConte
CDM and Milgrom's law

Milgrom noticed the remarkable fact that the gravitational effect of dark matter in galaxies only becomes important where accelerations are less than about 10^{-8} cm / s^2 ~ cH_0\$ (Milgrom's Law''). This forms the basis for Modified Newtonian Dynamics (MOND), an alternative to particle dark matter. We show that in the Cold Dark Matter (CDM) theory of structure formation Milgrom's Law comes about naturally.

January, 2002:

Jan. 29 , 12:30 pm
349 LeConte

December, 2001:
Dec. 11 , 11:30 am
Havard Sandvik
Imperial College
375 LeConte
"A simple varying alpha theory"
The talk concentrates on cosmological consequences of a simple scalar theory in which the fine structure constant, alpha, is allowed to vary. The theory is gauge and Lorentz invariant, and satisfies general covariance. Alpha is found to be constant in the radiation era, growing in the matter epoch and approaching a constant as vacuum energy takes over the expansion. The model satisfies geonuclear, nucleosynthesis and CMB constraints on time variation in alpha, while fitting simultaneously the recent high redshift evidence for small alpha variations in quasar spectra. The model also complies with fifth force experiments, and makes predictions on the nature of the dark matter. New anthropic arguments based on varying constant theories are also discussed.

Dec. 4 , 11:30 am
Neal Dalal
University of California, San Diego
375 LeConte
"Detection of CDM Substructure"

November, 2001:

November 20, 11:30 am
Berkeley Cosmology Group Lunch
LeConte 349 (CfPA Conference Room)
Bring your lunch and come ready to talk about cosmology. If no one has nothing in particular they want to discuss we can talk about astro-ph/0106399, Weak Lensing and Dark Energy, by D. Huterer

Nov. 13, 11:30 am
Rachel Bean
Imperial College
375 LeConte
"Constraining dark energy"
Cosmology is entering one of its most exciting episodes in the next couple of years, seeing an unprecedented improvement in the quantity and quality of data. With this in mind, we present new results updating the current constraints on the energy density and equation of state of dark energy. We critically consider how much can be currently inferred about the dynamical equation of state and how this may affect our observing strategies for the future.

November 6, 11:30 am
Berkeley Cosmology Group Lunch
LeConte 349 (CfPA Conference Room)
Bring your lunch and come ready to talk about cosmology. If no one has nothing in particular they want to discuss we can talk about astro-ph/0108013, Galaxy Mass and Luminosity Scaling Laws Determined by Weak Gravitational Lensing, McKay et al (full resolution version here.)

October, 2001:
October 23, 11:30 am
Berkeley Cosmology Group Lunch
LeConte 349 (CfPA Conference Room)
Bring your lunch and come ready to talk about cosmology. If no one has nothing in particular they want to discuss we can talk about astro-ph/0110353, Constraining dark energy with Sunyaev-Zel'dovich cluster surveys by Jochen Weller, Richard Battye, Ruediger Kneissl

October 9, 12:30 pm
Eric Gawiser
University of California at San Diego
"Towards A Complete Picture of Damped Lyman Alpha Systems"

Abstract:
Damped Lyman alpha absorption systems (DLAs) contain most of the neutral hydrogen in the high-redshift universe and are the likely progenitors of typical galaxies like the Milky Way. Nonetheless, it is not yet clear whether DLAs are massive galaxies or low-mass protogalaxies, or whether they are connected with the Lyman break galaxies or represent a separate population. I will present results from an observational program designed to clarify the DLA picture. Neither the fraction of the matter density comprised by neutral hydrogen nor the metallicity of the universe as probed by DLAs evolves from z=4 to z=2. Dust extinction does not appear to bias these measurements significantly. The cosmic star formation rate measured in DLAs is comparable to that of Lyman break galaxies and may explain the observed excess of the Near Infrared Background radiation. Finally, I will describe an ongoing effort to determine the mass of DLAs by studying their cross-correlation with Lyman break galaxies.

Past CfPA Seminars in 2001-2002 Academic Year

Past CfPA Seminars in 2000-2001 Academic Year

Past CfPA Seminars in 1999

Past CfPA Seminars in 1998

Past CfPA Seminars in 1997

Past CfPA Seminars in 1996