Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session H10: Classical and Semiclassical Gravity |
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Sponsoring Units: GGR Chair: Jorge Pullin, Louisiana State University Room: Governor's Square 12 |
Sunday, April 14, 2013 10:45AM - 10:57AM |
H10.00001: Near-Horizon Conformal Symmetry Revisited Steven Carlip In addition to diffeomorphism invariance, any equilibrium black hole spacetime admits a local conformal invariance near the horizon. I revisit and revise a proposal that this symmetry governs the density of states of the black hole. [Preview Abstract] |
Sunday, April 14, 2013 10:57AM - 11:09AM |
H10.00002: Imaginary action and gravitational entropy Yasha Neiman We present a candidate for a new derivation of black hole entropy. We begin by examining the on-shell action of gravity in bounded regions of spacetime. A careful consideration of the boundary term reveals an imaginary part, whose form resembles the formula for gravitational entropy. For stationary black hole solutions, we identify families of bounded regions for which the action's imaginary part precisely equals the black hole entropy. Thus, we have a fully Lorentzian calculation, with no assumption of stationarity and no reference to asymptotic infinity, which reproduces the known entropy formula for stationary black holes. The calculation is carried out for General Relativity with cosmological constant and minimally-coupled matter, as well as for Lovelock gravity. The results represent a step towards understanding gravitational entropy in non-stationary and cosmological contexts. [Preview Abstract] |
Sunday, April 14, 2013 11:09AM - 11:21AM |
H10.00003: Thermodynamics of a Black Hole with Moon Samuel Gralla, Alexandre Le Tiec For a rotating black hole perturbed by a particle on the ``corotating'' circular orbit (angular velocity equal to that of the event horizon), the black hole remains in equilibrium in the sense that the perturbed event horizon is a Killing horizon of the helical Killing field. The associated surface gravity is constant over the horizon and should correspond to the physical Hawking temperature. We calculate the perturbation in surface gravity/temperature, finding it negative: the moon has a cooling effect on the black hole. We also compute the surface area/entropy, and find no change from the background Kerr value. [Preview Abstract] |
Sunday, April 14, 2013 11:21AM - 11:33AM |
H10.00004: Near-Extremal Kerr $AdS_2\times S^2$ Solution and Black-Hole/Near-Horizion-CFT Duality Ananda Guneratne, Leo Rodriguez, Sujeev Wickramasekara, Tuna Yildirim We study the thermodynamics of the near horizon of near extremal Kerr geometry ($near-NHEK$) within an $AdS_2/CFT_1$ correspondence. We do this by shifting the horizon by a general finite mass, which does not alter the geometry and the resulting solution is still diffeomorphic to $NHEK$, however it allows for a Robertson Wilczek two dimensional Kaluza-Klein reduction and the introduction of a finite regulator on the $AdS_2$ boundary. The resulting asymptotic symmetry group of the two dimensional Kaluza-Klein reduction leads to a non-vanishing quantum conformal field theory ($CFT$) on the respective $AdS_2$ boundary. The $s$-wave contribution of the energy-momentum-tensor of the $CFT$, together with the asymptotic symmetries, generate a Virasoro algebra with calculable center and non-vanishing lowest Virasoro eigen-mode. The central charge and lowest eigen-mode reproduce the $near-NHEK$ Bekenstein-Hawking entropy via the statistical Cardy Formula and our derived central charge agrees with the standard Kerr/$CFT$ Correspondence. We also compute the Hawking temperature of the shifted $near-NHEK$ by analyzing quantum holomorphic fluxes of the Robinson and Wilczek two dimensional analogue fields. [Preview Abstract] |
Sunday, April 14, 2013 11:33AM - 11:45AM |
H10.00005: SUSY Schwarzschild and Schwarzschild-(anti)de Sitter black holes O. Obregon, S. Zacarias, J.C. Lopez-Dominguez The Wheeler-DeWitt (WDW) equation for the Kantowski-Sachs model can also be understood as the WDW equation corresponding to the Schwarzschild black hole due to the well known diffeomorphism between these two metrics. The WDW equation and its solutions are ignorant of the coordinate patch one is using, only by imposing coordinate conditions we can differentiate between cosmological and black hole models. At that point, the foliation parameter $t$ or $r$ will appear in the solution of interest. We supersymmetrize this WDW equation obtaining an extra term in the potential with two possible signs. The WKB method is then applied, giving rise to two classical equations. Two asymptotic cases arise; one of them corresponds to the usual Schwarzschild black hole. We study the other two asymptotic regions; they provide three singular solutions at $r=0$ and depending on an integration constant $C$ they can also present a singularity in $r=C^2$. We find an associated mass, and based on the holographic principle an entropy can be assigned to this asymptotic solution. The same procedure is applied to the Lambda-Kantowski-Sachs model, its WDW equation can also be understood as the one corresponding to the Schwarzschild-(anti)de Sitter space-times. These cases will also be discussed. [Preview Abstract] |
Sunday, April 14, 2013 11:45AM - 11:57AM |
H10.00006: Density Density Correlation Function for a Bose-Einstein Condensate Analog Black Hole Paul Anderson, Roberto Balbinot, Alessandro Fabbri, Renaud Parentani The density density correlation function is computed for an analog black hole which consists of a Bose-Einstein condensate with an acoustic horizon. The method used relies only on quantum field theory in curved spacetime techniques. A comparison with the results obtained by ab initio full condensed matter calculations is given, confirming the validity of the approximation used provided the profile of the flow varies smoothly on scales compared to the condensate healing length. [Preview Abstract] |
Sunday, April 14, 2013 11:57AM - 12:09PM |
H10.00007: Configurational Entropy of Perturbed Classical Systems Damian Sowinski, Marcelo Gleiser The canonical way of building theories in physics relies heavily on Hamilton's principle of least action. The resulting classical solution to a given theory is one whose energy is minimized; any perturbation to the solution results in an increase in its energy. The question is whether there are other quantities that are extremized by the variational principle, including gravitationally bound systems. Recently, Gleiser and Stamatopoulos have investigated a novel physical quantity defined in Fourier space, Configurational Entropy (CE), in several non-gravitational settings. Classical solutions for non-periodic potentials seem to imply that this quantity is indeed minimized under a wide range of trial functions that attempt to emulate them. Here we investigate the spectrum of perturbations to classical solutions of Newtonian and generally-relativistic gravitationally-bound systems and their effect on the CE. In particular, for stellar polytropes we show how the minimum of the CE is minimized for polytropic index related to tightly-bound compact objects and how it can be used to indicate the onset of gravitational instability. [Preview Abstract] |
Sunday, April 14, 2013 12:09PM - 12:21PM |
H10.00008: Relativity of Scale: Emergence of Quantum Behavior from Space-Time Geometry and Its Implications Shantikumar Nair The paper presents the principles of the relativity of scale - a new principle which relates the nature of the space-time background to the mass and size of a particle relative to the observer. The study shows that quantum behavior can evolve from the dynamic space-time background of general relativity. In principle then it is possible to construct a complete quantum theory based on general relativity. The paper further shows that around sufficiently small particles space-time can be substantially curved giving rise to time dilation and space contraction effects as with particles moving at high velocities. The forces calculated from the space-time geometry is fully consistent with known electromagnetic forces suggesting that this can be a new approach to unify the quantum world with the macroscopic world governed by general relativity. [Preview Abstract] |
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