Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session E7: Cosmology III |
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Sponsoring Units: DAP Room: Hyatt Regency Dallas Pegasus A |
Saturday, April 22, 2006 3:30PM - 3:42PM |
E7.00001: Singular behavior in Lema\^{i}tre-Tolman-Bondi cosmological models and the difficulties in using them as realistic models of the Universe Ali Vanderveld, Eanna Flanagan, Ira Wasserman There has been much debate over whether or not one could explain the observed acceleration of the Universe with inhomogeneous cosmological models, such as the spherically-symmetric Lema\^{i}tre-Tolman-Bondi (LTB) models. It has been claimed that the central observer in these models can observe a local acceleration, which would contradict general theorems. We resolve the contradiction by noting that many of the models that have been explored contain a weak singularity at the location of the observer, which makes them unphysical. In the absence of this singularity, we show that LTB models must have a positive central deceleration parameter $q_{0}$, in agreement with the general theorems. We also show that at nonzero redshifts the apparent deceleration parameter measured by the central observer can be negative. However, we find other singularities that tend to arise in LTB models when attempting to match luminosity distance data, and these generally limit the range of redshifts for which these models can mimic observations of an accelerating Universe. [Preview Abstract] |
Saturday, April 22, 2006 3:42PM - 3:54PM |
E7.00002: In Search of B-modes: Deconvolution Map-Making for CMB Polarization Observations Charmaine Armitage, Benjamin Wandelt The upcoming Planck satellite will provide new cosmological information contained in precision measurements of the polarization of the Cosmic Microwave Background (CMB) anisotropies. In particular, a measurement of the B-mode polarization would probe inflationary gravitational waves. Several challenges are faced in measuring this B-mode: the signal is tiny compared to the temperature anisotropies, and it is difficult to separate the E-mode from the B-mode. Thus, we expect that polarimetry experiments will be very sensitive to beam asymmetries and stray light. Deconvolution map-making (Armitage \& Wandelt 2004) removes systematic effects due to beam asymmetries by solving the maximum-likelihood map-making problem for arbitrary beams. We compare results from our method with a standard map-making method and demonstrate that the true sky is recovered with high accuracy via the deconvolution method. We also consider foregrounds and show the effects of ignoring beam asymmetries on the reconstruction of point sources. [Preview Abstract] |
Saturday, April 22, 2006 3:54PM - 4:06PM |
E7.00003: Black Hole Formation during a Cosmological QCD Phase Transition Todd Springer, Joseph Kapusta The formation of primordial black holes from density fluctuations is usually thought to be relatively rare due to the large over-density required to overcome pressure forces and cause a collapse. In recent years, work has been done to examine whether the effect of a quark-hadron phase transition could reduce the necessary over-density due to a softening of the equation of state. Previous analyses have focused on a first order phase transition using a bag model equation of state. Using a combination of semi-analytic and numerical approaches, we examine this issue for equations of state that exhibit a first order phase transition, a second order phase transition, or just a rapid crossover. We find there is an enhanced production of sub-solar mass black holes even if the transition is not first order. [Preview Abstract] |
Saturday, April 22, 2006 4:06PM - 4:18PM |
E7.00004: Force-free Magnetosphere of a Kerr Black Hole and Energy Extraction Govind Menon, Charles Dermer Recent results on the electrodynamics of Black Holes will be discussed using the 3+1 (space and global time) formalism. This formalism has permitted the construction of an exact class of solutions to the Blandford-Znajek mechanism. Physical properties of the exact solution are analyzed following which the nature of jet formation and energy extraction from Kerr Black Holes will be presented. [Preview Abstract] |
Saturday, April 22, 2006 4:18PM - 4:30PM |
E7.00005: CMB Tomography: Reconstruction of Adiabatic Primordial Scalar Potential Using Temperature and Polarization Maps. Amit P. S. Yadav, Benjamin D. Wandelt Assuming linearity of the perturbations at the time of decoupling, we reconstruct the primordial scalar potential from the temperature and polarization anisotropies in the cosmic microwave background radiation. In doing so we derive an optimal linear filter which, when operated on the spherical harmonic coefficients of the anisotropy maps, returns an estimate of the primordial scalar potential fluctuations in a spherical slice. The reconstruction is best in a thick shell around the decoupling epoch; the quality of the reconstruction depends on the redshift of the slice within this shell. With high quality maps of the temperature and polarization anisotropies it will be possible to obtain a reconstruction of potential fluctuation on scales between $\ell=2$ and $\ell \sim 300$ at the redshift of decoupling, with some information about the three-dimensional shapes of the perturbations in a shell of width 250Mpc. The main motivation for reconstructing primordial perturbations is to study the non-Gaussianities in the initial conditions. Reconstruction allows us to be more sensitive to the primordial perturbations, which is important because current detections of non-Gaussianity do not specifically select for the primordial perturbations. [Preview Abstract] |
Saturday, April 22, 2006 4:30PM - 4:42PM |
E7.00006: Gravitational lensing by 3-d matter distributions Thomas Kling Gravitational lensing studies have become an important tool for studying galactic structure and cluster morphology because the methods do not rely heavily on specific knowledge of cosmological parameters. To date, lensing studies use a weak- field, thin lens approximation where the lensing action is assumed to occur in a two-dimensional lens plane. We compare this approximation with the results of integrating the null geodesic equations for weak field metrics with ``standard'' three dimensional mass distributions. [Preview Abstract] |
Saturday, April 22, 2006 4:42PM - 4:54PM |
E7.00007: The Large Synoptic Survey Telescope Project David Gilmore The prime goal of LSST is a precision measure of the nature of dark energy though a suite of techniques using a homogeneous imaging dataset. Central of these is weak lens shear of galaxy shapes to z=3 by mass at z$<$3, giving a unique probe of dark energy. This will be done through a combination of deep-wide multi-band imaging data over 20,000 sq.deg. in a weak lensing survey of unprecedented sensitivity, volume and quality. LSST will be a large, wide-field groundbased telescope designed to obtain sequential images of the entire visible sky every few nights. The optical design involves a 3-mirror system with an 8.4 m primary, which feeds three refractive correcting elements inside a camera, providing a 10 square degree field of view sampled by a 3 Gpixel focal plane array. The total effective system throughput, A$\Omega $ = 318 m 2 deg2, is nearly two orders of magnitude larger than that of any existing facility. The survey will yield contiguous overlapping imaging of 20,000 -- 23,000 square degrees of sky in 6 optical bands covering the wavelength regime 350--1100 nm. [Preview Abstract] |
Saturday, April 22, 2006 4:54PM - 5:06PM |
E7.00008: Magnitude-Redshift Relation for Supernovae Ia, Time Dilation, and Plasma Redshift. Ari Brynjolfsson Using conventional axioms of physics, the plasma redshift follows from exact evaluation of photons interaction with hot sparse electron plasma, as shown by Brynjolfsson in arXiv:astro- ph/0401420. We have previously used the supernovae data by Riess et al. to show that they match the prediction of the magnitude-redshift relation in plasma-redshift cosmology. In the present article, we use the most recent SNLS data, which have slightly narrower distribution, as reported by Astier et al. in 2005, to show that also these data match the predictions of the plasma redshift. The comparison indicates that consistent with plasma-redshift cosmology there is no cosmological time dilation and no Big Bang. There is no need for Dark Energy or Dark Matter. The plasma redshift predicts also significant intrinsic redshifts of stars, galaxies, and quasars consistent with that observed. Plasma redshift predicts well not only the observed magnitude-redshift relation for supernovae Ia, also the observed cosmic microwave background (CMB), and the cosmic X-ray background. The Hubble constant is about 62.6 km per sec per Mpc. [Preview Abstract] |
Saturday, April 22, 2006 5:06PM - 5:18PM |
E7.00009: The shrinking Hubble constant. Russell Collins The extraction of the Hubble constant from a plot of the measured distance of stellar objects vs. red shift Z is flawed in 3 ways. Distances must be extrapolated to present time. The Doppler portion of the red shift must be found. The gravitational changes of the metric through which the light passes must be accounted for. Using a model of the big bang as a sphere of radius R=cT, with uniform density and absent acceleration, extrapolation is had by multiplying distance by 1+$\beta$. The red shift can be separated into Doppler and gravitational components, upon recognizing that the time of the event, T*, connects them. The gravitational potential decreases as the big bang expands, and this affects the measured optical distance. Correction is had using mass-metric relativity (arxiv physics/0012059), and fully accounts for curvature in high Z Hubble plots. Using a data set to Z=1.2 by Riess (AJ/journals/v116n3/980111), one finds T=23.5 billion years (Ho=41.6). This is older than the present consensus value, T=14 billion years (Ho=71). Plotted correctly as present distance vs. velocity, a linear Hubble plot is obtained. Full details at arxiv physics/0601013. [Preview Abstract] |
Saturday, April 22, 2006 5:18PM - 5:30PM |
E7.00010: Initial Conditions for Cosmic Evolution Using GRMHD Equations David Garrison, Cindi Ballard, John Hamilton Numerically evolving the early universe after the inflationary expansion period requires a method of handling the Smoothness problem. Through the use of GRMHD turbulence it should be possible to show that structure formation can occur without violating the Smoothness condition or introducing concepts such as Imperceptibly Unsmooth Smoothness or Quantum Vacuum Energy Fluctuations. An attempt to solve Einstein's equations coupled with the equations of General Relativistic Magnetohydrodynamics for a smooth plasma is being made at the University of Houston Clear Lake. The challenge of this work is to identify the initial conditions for the standard model that lead to the development of the observed mass concentration in clusters and super clusters of galaxies. The initial conditions were selected so that alignment with observed values of the spectrum and isotropy of the cosmic background radiation are preserved as one evolves forward in time. This work presents the derivation of the initial conditions as well as the assumptions leading to them. [Preview Abstract] |
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