Bulletin of the American Physical Society
Joint Fall 2011 Meeting of the Texas Sections of the APS, AAPT, and Zone 13 of the SPS
Volume 56, Number 7
Thursday–Saturday, October 6–8, 2011; Commerce, Texas
Session L6: Cosmology & General Relativity |
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Chair: Mario Diaz, University of Texas at Brownsville Room: Science Building 122 |
Saturday, October 8, 2011 9:25AM - 9:37AM |
L6.00001: Universal Behavior in Inflationary Cosmology Sean Downes Inflation is studied using a Singularity Theory, resulting in a set of universality classes with distinct quantitative behavior. The physical observables are shown to be insensitive to the model-dependent details. This strongly suggests inflation is an emergent behavior. Examples from IIB string theory and the supersymmetric field theories are given. Finally, the problem of initial conditions is addressed in the context of the overall probability of inflation. [Preview Abstract] |
Saturday, October 8, 2011 9:37AM - 9:49AM |
L6.00002: Cosmology in One-dimension: Correlation, Virialization and Void Geometry Bruce Miller, Jean-Louis Rouet Concentrations of matter in the universe, such as galaxies and galactic clusters, originated as very small density fluctuations in the early universe. The existence of galaxy clusters and super-clusters suggests that a natural scale for the matter distribution may not exist. A point of controversy is whether the distribution is fractal and, if so, over what range of scales. Even with recent astronomical surveys and simulations, it is difficult to extract information concerning fractal properties with confidence. With one-dimensional models we can overcome these limitations by carrying out simulations with on the order of a quarter of a million particles. They clearly demonstrate that the important dynamics for cluster formation occurs in the position-velocity plane. Here we present the recent results of our on-going study of the fractal geometry of one dimensional models of the expanding universe. The evolution of the power spectra and correlation function will be followed and their relation to the correlation dimension will be explored. Evidence of the development of virialization and an improved approach for determining the fractal dimensions of low density regions (voids) will be presented. [Preview Abstract] |
Saturday, October 8, 2011 9:49AM - 10:01AM |
L6.00003: Time Rate and Light Speed in Variable Motion Spaces Penglin Yang This paper presents a transformation that applies to variable motion spaces, which is different from the Lorentz transformation that described uniform motion spaces in the Einstein's Special Theory of Relativity. In the new transformation, the two equations which describe two coordinates or variable motion spaces, can transform from one into another. Furthermore, from the transformation, no matter how two spaces relatively move--variable speed or constant speed, the light speed in either space is constant, which is observed from its own view. But from a third view, the light speeds in the two spaces are not constant. [Preview Abstract] |
Saturday, October 8, 2011 10:01AM - 10:13AM |
L6.00004: A Figure of Merit Analysis of Current Constraints on Testing General Relativity using the Latest Cosmological Data Sets Jason Dossett, Jacob Moldenhauer, Mustapha Ishak Currently, much attention is going into testing general relativity to see if cosmic acceleration is due to dark energy or a modification to gravity at cosmological scales. An increasingly popular approach to this problem is parameterizing modifications to the growth equations in general relativity, particularly the Poisson's equation and the ratio between the two metric potentials in the perturbed FLRW metric. We compare some of the various modified growth (MG) parameterizations that have been proposed in recent literature. Next we place constraints on the MG parameters using current cosmological data. A Figure of Merit approach is then used to study and compare the constraining power of various combinations of data sets on the MG parameters. We find that adding up current data sets does not consistently improve the uncertainties on MG parameters due to tensions between the best-fit MG parameters preferred by different data sets. Finally, for all the parameterizations used, we find that the values corresponding to general relativity are within the 95{\%} confidence level contours for all data set combinations. [Preview Abstract] |
Saturday, October 8, 2011 10:13AM - 10:25AM |
L6.00005: Searching for the ``Fifth Force'' with the Spectrum of Gravitational Wave Signals from Oscillating Neutron Stars Weikang Lin What information about the ``fifth force'' could be drawn from the gravitational waves signals? As long as the maximum mass of the neutron star is concerned, there is a degeneracy between the uncertainty in nuclear matter properties and the uncertainty in the gravity, since the soft EOS can also produce a large enough maximum mass under the effect of Yukawa term. We investigated the Yukawa-term-modified gravity on the mode oscillation frequencies of non-rotating neutron stars. The existence of Yukawa term could bring down significantly the mode oscillation frequencies. The distinct effect on stellar mode oscillation frequencies would help to solve the above degeneracy. While there have been some experiments to search and set constraints on the ``fifth force,'' we state that the gravitational wave detection would open a new approach to this problem. [Preview Abstract] |
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