Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session S12: Cosmology: Observation, Interpretation, Large Scale Structure |
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Sponsoring Units: DAP Chair: Chanda Prescod-Weinstein, MIT Room: 250DE |
Monday, April 18, 2016 1:30PM - 1:42PM |
S12.00001: Cosmology with kinematic Sunyaev-Zel'dovich effect measurements from ACTPol and future surveys. Francesco De Bernardis ACTPol is the first polarization receiver for the Atacama Cosmology Telescope (ACT) that is observing the CMB sky with arcmin resolution over about 2000 sq. deg. Its upgrade, Advanced ACTPol, will observe the CMB in five frequency bands and over a larger area of the sky. These measurements will enable a number of astrophysical and cosmological studies. We focus on the kinematic SZ effect as measured through the mean pairwise momentum of galaxy clusters. The spectroscopic information is particularly valuable for these measurements and ACTPol is in a unique position for this kind of study due to its wide overlap with the Baryon Oscillation Spectroscopic Survey (BOSS). The pairwise kSZ signal is able to probe the growth and expansion history of the universe. Moreover, measurements of the kSZ effect can be used to test advanced hydrodynamical simulations of the Intra-Cluster Medium (ICM) and to constrain the baryon content of galaxy clusters. We report the latest kSZ results from ACTPol and BOSS and describe the potential strong constraints on cosmological parameters and practical challenges in the extraction and maximization of the signal-to-noise ratio. We discuss the main sources of systematic uncertainty and the progress towards realistic forecasts for future CMB instruments. [Preview Abstract] |
Monday, April 18, 2016 1:42PM - 1:54PM |
S12.00002: SPIDER: Listening for the echoes of inflation from above the clouds Jeffrey Filippini We report on the status of SPIDER, a balloon-borne instrument to map the polarization of the cosmic microwave background at large angular scales. SPIDER targets the B-mode signature of primordial gravitational waves, with a focus on mapping a large sky area at multiple frequencies. SPIDER’s six monochromatic refracting telescopes (three each at 95 and 150 GHz) feed a total of more than 2000 antenna-coupled superconducting transition-edge sensors. A sapphire half-wave plate at the aperture of each telescope modulates sky polarization for control of systematics. We discuss SPIDER’s first long-duration balloon flight in January 2015, as well as the status of data analysis and development toward a second flight. [Preview Abstract] |
Monday, April 18, 2016 1:54PM - 2:06PM |
S12.00003: Probing the Epoch Reionization at Redshifts 6 to 12 with MWA, PAPER and HERA Daniel Jacobs Direct observation of cosmological hydrogen throughout cosmic time is possible via the 21cm line and is now being pursued as a new cosmological and astrophysical probe. Multiple experimental low frequency radio arrays have worked towards detection and characterization of this spectral line signal through many different epochs of cosmic time. The Epoch of Reionization (EoR), when the first stars ionized the primordial hydrogen half a billion years after the big bang, thought to occur between redshifts 6 and 12 is a period of intense interest. The Precision Array for Probing the Epoch of Reionization (PAPER) has placed a series of ever more sensitive limits on the 21cm power spectrum while the Murchison Widefield Array (MWA) has pioneered imaging of structure in the presence of foregrounds. Here we present the latest results from these experiments and introduce the next generation Hydrogen Epoch of Reionization Array (HERA) which will yield 20 times the sensitivity of first generation arrays and provide new constraints on the nature of the first stars, the evolution of primordial galaxies, and significant new constraints on fundamental cosmological parameters. [Preview Abstract] |
Monday, April 18, 2016 2:06PM - 2:18PM |
S12.00004: ABSTRACT WITHDRAWN |
Monday, April 18, 2016 2:18PM - 2:30PM |
S12.00005: Fundamental Constants as Monitors of Particle Physics and Dark Energy Rodger Thompson This contribution considers the constraints on particle physics and dark energy parameter space imposed by the astronomical observational constraints on the variation of the proton to electron mass ratio $\mu$ and the fine structure constant $\alpha$. These constraints impose limits on the temporal variation of these parameters on a time scale greater than half the age of the universe, a time scale inaccessible by laboratory facilities such as the Large Hadron Collider. The limits on the variance of $\mu$ and $\alpha$ constrain combinations of the QCD Scale, the Higgs VEV and the Yukawa coupling on the particle physics side and a combination of the temporal variation of rolling scalar field and its coupling to the constants on the dark energy side. [Preview Abstract] |
Monday, April 18, 2016 2:30PM - 2:42PM |
S12.00006: Gravitational potential wells and the cosmic bulk flow Yuyu Wang, Abhinav Kumar, Hume Feldman, Richard Watkins The bulk flow is a volume average of the peculiar velocities and a useful probe of the mass distribution on large scales. The gravitational instability model views the bulk flow as a potential flow that obeys a Maxwellian Distribution. We use two N-body simulations, the LasDamas Carmen and the Horizon Run, to calculate the bulk flows of various sized volumes in the simulation boxes. Once we have the bulk flow velocities as a function of scale, we investigate the mass and gravitational potential distribution around the volume. We found that matter densities can be asymmetrical and difficult to detect in real surveys, however, the gravitational potential and its gradient may provide better tools to investigate the underlying matter distribution. This study shows that bulk flows are indeed potential flows and thus provides information on the flow sources. We also show that bulk flow magnitudes follow a Maxwellian distribution on scales $>10\ h^{-1}$ Mpc. [Preview Abstract] |
Monday, April 18, 2016 2:42PM - 2:54PM |
S12.00007: Multi-stream portrait of the Cosmic web Nesar Ramachandra, Sergei Shandarin We report the results of the first study of the multi-stream environment of dark matter haloes in cosmological N-body simulations in the $\Lambda$CDM cosmology. The full dynamical state of dark matter can be described as a three-dimensional sub-manifold in six-dimensional phase space - the dark matter sheet. In our study we use a Lagrangian sub-manifold ${\bf x} = {\bf x}({\bf q},t)$ (where ${\bf x}$ and ${\bf q}$ are co-moving Eulerian and Lagrangian coordinates respectively), which is dynamically equivalent to the dark matter sheet but is more convenient for numerical analysis. Our major results can be summarized as follows. At the resolution of the simulation, the cosmic web represents a hierarchical structure: each halo is embedded in the filamentary framework of the web predominantly at the filament crossings, and each filament is embedded in the wall like fabric of the web at the wall crossings. Locally, each halo or sub-halo is a peak in the number of streams field. The number of streams in the neighbouring filaments is higher than in the neighbouring walls. The walls are regions where number of streams is equal to three or a few. Voids are uniquely defined by the local condition requiring to be a single-stream flow region. [Preview Abstract] |
(Author Not Attending)
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S12.00008: Examining the Viability of Phantom Dark Energy Kevin Ludwick In the standard cosmological framework of the 0th-order FLRW metric and the use of perfect fluids in the stress-energy tensor, dark energy with an equation-of-state parameter $w < -1$ (known as phantom dark energy) implies negative kinetic energy and vacuum instability when modeled as a scalar field. However, the accepted values for present-day $w$ from Planck and WMAP9 include a significant range of values less than $-1$. Staying within the confines of observational constraints and general relativity, for which there is good experimental validation, we consider a few reasonable departures from the standard 0th-order framework in an attempt to see if negative kinetic energy can be avoided in these settings despite an apparent $w<-1$. We consider a more accurate description of the universe through the perturbing of the isotropic and homogeneous FLRW metric and the components of the stress-energy tensor, and we consider dynamic $w$ and primordial isocurvature and adiabatic perturbations. We find that phantom dark energy does not necessarily have negative kinetic energy for all relevant length scales at all times and, by the same token, that quintessence dark energy does not necessarily have positive kinetic energy for all relevant length scales at all times. [Preview Abstract] |
Monday, April 18, 2016 3:06PM - 3:18PM |
S12.00009: Modified Chaplygin Gas Cosmology from Geometrothermodynamics Hachemi Benaoum The modified Chaplygin gas (MCG) cosmological model is investigated in the context of geometrothermodynamics (GTD) formalism. We show that the MCG corresponds to a system with internal thermodynamic interaction and describes the current accelerated expansion of the universe. Moreover, we also note that the MCG as a unified model for dark energy and dark matter is perfectly consistent with the current SNe observations and CMB anisotropy measurements. [Preview Abstract] |
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