Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session E11: Quantum and Classical Gravity |
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Sponsoring Units: GGR Chair: Kevin Vandersloot, Pennsylvania State University Room: Hyatt Regency Dallas Cumberland E |
Saturday, April 22, 2006 3:30PM - 3:42PM |
E11.00001: Effects of nonzero neutrino masses on black hole evaporation William Hiscock, Daniel Bambeck We study the consequences of nonzero neutrino masses for black holes evaporating by the emission of Hawking radiation. We find that the evolution of small, hot, black holes may be unaffected (if neutrinos are Majorana particles), or may show an increase in neutrino luminosity and a decrease in lifetime by up to a factor of approximately $1.85$ (if neutrinos are Dirac particles). However, for sufficiently large ({\it e.g.}, stellar mass) black holes, nonzero masses result in neutrino emission being largely or entirely suppressed, resulting in a decrease in emitted power and an increase in lifetime by up to a factor of about $7.5$. [Preview Abstract] |
Saturday, April 22, 2006 3:42PM - 3:54PM |
E11.00002: Quantum effects in Spherically Symmetric Traversable Wormhole Spacetimes William Hirsch The expectation value of the full renormalized stress-energy tensor operator,$\langle T_{\mu\nu}\rangle$, has been calculated for a number of spherically symmetric wormhole spacetimes for the massless fermion field. One metric describes a phantom energy wormhole. The wormholes are at zero temperature. The components of $\langle T_{\mu\nu}\rangle$ are then examined to determine if the wormhole geometries are stable for various values of the renormalization parameter $\mu$. [Preview Abstract] |
Saturday, April 22, 2006 3:54PM - 4:06PM |
E11.00003: Back Reaction of the Hawking Radiation Cecile DeWitt-Morette Three fundamental papers by G.A. Vilkovisky: ``Kinematics of evaporating black holes,'' ``Radiation equations for black holes,'' and ``Backreaction of the Hawking radiation'' (respectively available from arXiv:hep-th/0511182/3/4) present the calculation of the evolution of black holes driven by the Hawking radiation. The solution of the backreaction problem is a generalization of the Schwarzschild metric. Bryce DeWitt had been hoping that the solution of the backreaction problem would be obtained in time for him to include it in his book ``The Global Approach to Quantum Field Theory'' The Hawking radiation and its backreaction are semiclassical effects. According to Vilkovisky, blackloles create a ``vacuum matter charge'' to protect themselves from the quantum evaporation. A spherically symmetric black hole having initially no ``matter charges'' radiates away about 10{\%} of the initial mass and comes to a state in which the vacuum-induced charge equals the remaining mass. The metric in the semiclassical region of the collapse spacetime is obtained and studied. I shall present and discuss Vilkovisky's work. [Preview Abstract] |
Saturday, April 22, 2006 4:06PM - 4:18PM |
E11.00004: Quantum Gravity Modulates Fermion Field Strength during Inflation Richard Woodard, Shun-Pei Miao Because gravitons are massless without being conformally invariant, they engender enormously enhanced effects during inflation. One such effect is to alter the wave function of massless fermions by a time dependent field strength renormalization which would, if unchecked at higher loops, eventually convert positive norm particles into ghosts! We prove this by solving the effective field equations for massless fermions using the recently computed one loop self-energy for Gravity + Dirac (gr-qc/0511140). The Schwinger-Keldysh formalism is used to keep the results real and causal. It is curious that our result agrees, up to a numerical factor, with the Hartree-Foch approximation of simply taking the expectation value of the Dirac Lagrangian in the graviton vacuum. [Preview Abstract] |
Saturday, April 22, 2006 4:18PM - 4:30PM |
E11.00005: Quantum mechanical healing of classical singularities Deborah A. Konkowski, Thomas M. Helliwell How effective is quantum mechanics at healing classical spacetime singularities? A maximal spacetime has a classical singularity if it contains incomplete geodesics, while it has a quantum singularity if the propagation of a quantum wave packet is ill posed (in particular, if the Klein-Gordon wave operator is not essentially self-adjoint). We consider a wide class of classically singular spacetimes whose metric coefficients, as the singularity is approached, become power laws in one of the spatial coordinates. We then determine the range of exponents for which quantum-mechanical particles are unable to detect the classical singularity so that the corresponding spacetimes are quantum-mechanically nonsingular. [Preview Abstract] |
Saturday, April 22, 2006 4:30PM - 4:42PM |
E11.00006: Quantum Geometrodynamics of the Bianchi IX Cosmological Model Ruslan Vaulin, Arkady Kheyfets, Warner Miller The canonical quantum theory of gravity -- Quantum Geometrodynamics (QG) is applied to the homogeneous Bianchi type IX cosmological model. As a result, the framework for the quantum theory of homogeneous cosmologies is developed. We show that the theory is internally consistent, and prove that it possesses the correct classical limit (the theory of general relativity). We show that, unlike the traditional approaches, QG leads to a well-defined Schrodinger equation for the wave- function of the universe that is inherently coupled to the expectation value of the constraint equations. This coupling to the constraints is responsible for the appearance of a coherent spacetime picture. Thus, the physical meaning of the constraints of the theory is quite different from Dirac's interpretation. In light of this distinctive feature of the theory, we readdress the question of the dark energy effects in the Bianchi IX cosmological model for highly non-classical quantum states. [Preview Abstract] |
Saturday, April 22, 2006 4:42PM - 4:54PM |
E11.00007: Nambu-Goldstone Modes in Theories with Spontaneous Lorentz Violation Robert Bluhm, Alan Kostelecky The fate of the Nambu-Goldstone (NG) modes is examined in gravitational theories with spontaneous Lorentz violation. It is shown that the NG modes due to spontaneous Lorentz and diffeomorphism breaking can be naturally incorporated into the theory using a vierbein approach. The question of whether a Higgs mechanism occurs is examined as well. Vector models with spontaneous Lorentz violation called bumblebee models are used as an example. [Preview Abstract] |
Saturday, April 22, 2006 4:54PM - 5:06PM |
E11.00008: Energy Localization and the Taub Solution Paul Halpern In an attempt to define the localized distribution of energy, Einstein proposed the first energy-momentum complex, which would eventually be followed by other measures proposed by Tolman, Landau-Lifshitz and others. Recent years have brought a revival of interest in these methods, following Bondi's 1990 result that energy must in principle be localizable, and the 1996 finding by Aguirregabiria, Chamorro and Virbhadra that for any metric of the Kerr-Schild class, various prescriptions for the energy-momentum complex yield precisely the same distribution. This talk will focus on anisotropic cosmological solutions, particularly Taub's 1951 exact solution for a Bianchi type-IX geometry, and compare the results for several different energy-localization prescriptions, showing that these yield reasonable and well-defined results. We'll comment on how these findings bear on Cooperstock's hypothesis about gravitational radiation. [Preview Abstract] |
Saturday, April 22, 2006 5:06PM - 5:18PM |
E11.00009: Unifying Gravity and EM: A Riddle You Can Solve Douglas Sweetser Apply three rules to this riddle:\\ 1. Start from standard theory\\ 2. Work with quantum mechanics\\ 3. No new math\\ Start from the vacuum Hilbert-Maxwell action: \[S_{H-M}=\int\sqrt{-g}d^4x(R-\frac{1}{4c^2}(\nabla^{\mu} A^{\nu}-\nabla^{\nu}A^{\mu})(\nabla_{\mu}A_{\nu}-\nabla_{\nu}A_{\mu}))\] The Hilbert action cannot be quantized, so drop the Ricci scalar. To do more than EM, use an asymmetric tensor: \[S_{GEM}=\int\sqrt{-g}d^4x\frac{1}{4c^2}\nabla^{\mu}A^{\nu}\nabla_{\mu}A_{\nu} \] The metric is fixed up to a diffeomorphism. With a constant potential, the Rosen metric solves the field equations, is consistent with current tests, but predicts 0.7 $\mu$arcseconds more bending around the Sun than GR. Gauge symmetry is broken by the mass charge of particles. [Preview Abstract] |
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