KICP Colloquia

January 9, 2013 | 15:30, BSLC 115
Covering the Bases
Marc Kamionkowski, Johns Hopkins University
Note: Refreshments begin at 3:00 pm in LASR conference room.
One of the principal aims of cosmology today is to seek subtle correlations in primordial perturbations, beyond the standard two-point correlation that has been mapped precisely already, that may hint at new physics beyond that in the simplest single-field slow-roll models. I will describe in this talk a new class of such correlations and how they may be sought with galaxy surveys and in the CMB. I will then turn my attention to a new formalism, total-angular-momentum (TAM) waves, that my collaborators and I have recently developed. In most of the literature, cosmological perturbations are decomposed into Fourier modes, or plane waves. However, for calculations that aim to produce predictions for angular correlations on a spherical sky, a decomposition into TAM waves provides a far more direct and intuitive route from theory to observations. I will describe the formalism and illustrate with applications to cosmic shear, three-point correlation functions, and redshift-space distortions.

January 23, 2013 | 15:30, BSLC 115
New CMB Results from the South Pole Telescope
Ryan Keisler, University of Chicago
Note: Refreshments at 3:15pm in the LASR Conference Room
The South Pole Telescope (SPT) recently completed a 2500 square degree survey of the sky in the 3mm, 2mm and 1.4 mm bands with an unprecedented combination of resolution, area, and sensitivity. The data from this survey has enabled a number of studies, including the most precise measurement of the sub-degree primordial CMB anisotropy to date. This talk will review this measurement and the resulting cosmological constraints. The new SPT data, in conjunction with data from the WMAP satellite and low-redshift measurements, leads to strong constraints on the number of neutrino-like particle species present in the early universe, the sum of the neutrino masses, and the shape of the power spectrum of primordial density fluctuations. I will also give a brief update on the status of SPTpol, the new polarization-sensitive receiver on the SPT.

February 13, 2013 | 15:30, BSLC 115
CMB Results from WMAP and ACT
Mark Halpern, University of British Columbia
Note: Refreshments begin at 3:00 pm in LASR conference room.
Acoustic processes in the plasma which pervades the early Universe govern the shape of the anisotropy of the cosmic background which has been measured by WMAP and other probes, notably ACT and the South Pole Telescope. I'll describe what we have learned, and what we have not learned from precise measurements of the temperature and polarization anisotropy of the CMB. Once the Universe became transparent, these acoustic signals stopped propagating. The density variations associated with them have remained fixed in co-moving (expanding) coordinates. I'll finish by talking about CHIME, the Canadian Hydrogen Intensity Mapping Experiment, CHIME, a collaboration to build a novel radio telescope designed to measure these same acoustic features at the much later epoch when cosmic acceleration from dark energy is important.

February 27, 2013 | 15:30, BSLC 115
Shedding light on dark matter and astrophysical sources with gamma-ray anisotropy
Jennifer Siegal-Gaskins, Caltech
Note: Refreshments begin at 3:00 pm in LASR conference room.
Gamma rays probe the most energetic processes in the universe and are a promising tool to search for signatures of new physics. One current mystery in high-energy astrophysics is the origin of the diffuse gamma-ray background. The contribution of undetected sources is expected to induce small-scale anisotropies in this emission, and these may provide a means of identifying and constraining the properties of its contributors. I will review the results of the first anisotropy analysis of the diffuse gamma-ray background measured by the Fermi Large Area Telescope, and highlight the new constraints this measurement has placed on high-energy source populations, focusing on implications for blazar population models and for a signal from the annihilation or decay of dark matter particles. I will also present new multi-wavelength techniques for unraveling contributors to diffuse emission.

March 6, 2013 | 15:30, BSLC 115
The secret lives of galaxy clusters
Brian W O'Shea, Michigan State University
Note: Refreshments begin at 3:00 pm in LASR conference room.
Galaxy clusters have the potential to be highly accurate probes of cosmological parameters. However, they are also very interesting astrophysical objects in their own right! The properties that make clusters irritating to those who wish to use them for cosmology - deviations from sphericity and hydrostatic equilibrium, shocks, mergers, and a variety of baryonic processes - provide a tremendous amount of information about these massive beasts. I will present recent efforts to understand the effects that correctly modeling the properties of gas in cosmological simulations have on the observable properties of clusters, focusing on shocks and the non-thermal components of the intracluster medium, including cosmic rays and magnetic fields.

April 3, 2013 | 15:00, BSLC 115
Towards 1% measurements of cosmological distances with cosmic sound
Nikhil Padmanabhan, Yale University
Note: Wine & Cheese Reception at 4:00 PM in the LASR Conference room
Measuring the accelerated expansion of the Universe with the goal of better understanding its underlying physics is one of the leading programs in cosmology today. The baryon acoustic oscillation technique is one of the foremost tools in our toolbox today. This talk will explain the underlying physics of this method and the reasons it is extremely robust to observational and theoretical systematic errors. I will then present the latest results from the SDSS and BOSS surveys, currently the most precise distance constraints from this method. These will include a new analysis technique to undo the effects of the nonlinear evolution of the density field and partially "reconstruct" the initial density field, and can reduce the distance errors by a factor of 1.7. I will discuss the implications of these measurements, and will conclude by discussing prospects for improvements in the immediate and not-so-immediate future.

April 10, 2013 | 15:00, BSLC 115
Effective Field Theories for Fluids and Superfluids
Alberto Nicolis, Columbia University
Note: Reception at 4:00 PM in the LASR Conference room
I will present a novel field theoretical framework that captures the long-distance and low frequency dynamics of hydrodynamical systems. The approach is that of effective field theories, whose building blocks are the long-distance degrees of freedom and symmetries. Possible applications include questions in condensed matter physics, heavy-ion collisions, astrophysics, cosmology, and quantum hydrodynamics. Finally, this formulation naturally invites (and answers) new questions in classical hydrodynamics.

April 16, 2013 | 15:00, BSLC 109
Cosmological Parameters from Planck and Other Experiments
George Efstathiou, University of Cambridge
Note: Wine and cheese reception following talk (4:00 - 5:00pm) in the LASR Conference Room
Joint Special Colloquium hosted by KICP, A&A and Physics.

May 1, 2013 | 15:00, BSLC 115
Dark Matter at Colliders
Shufang Su, University of Arizona
Note: Reception at 4:00 PM in the LASR Conference room.
While 27% of the Universe is made of dark matter, the particle identity of the dark matter still remains a mystery. Collider studies offers a complementary tool to explore the nature of the dark matter, in addition to dark matter direct and indirect detections. In this talk, I will discuss the collider studies of the dark matter, focusing on how to observe dark matter signals, and how to distinguish dark matter scenarios. In the first part of the talk I will discuss the model-independent approach for the monojet/monophoton plus missing ET signals, as well as model-dependent signatures of dark matter produced in the cascade decay chain of parent particles. The second part of the talk will focus on the study of distinguishing multiple component dark matter with traditional single particle dark matter.