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 M15: Quantum Aspects of Gravitation II |
Hide Abstracts |
Sponsoring Units: GGR Chair: Jorge Pullin, Louisiana State University Room: 251C |
Sunday, April 17, 2016 3:30PM - 3:42PM |
M15.00001: Phenomenology of loop quantum cosmology and observational consequences Brajesh Gupt An important feature of singularity resolution in loop quantum cosmology (LQC) is the occurrence of the quantum bounce when the spacetime curvature becomes Planckian leading the pre-inflationary evolution of the universe to be greatly modified. Due to the modified dynamics in the pre-inflationary era the initial conditions for both the background and cosmological perturbations are different from those in the standard inflationary scenario. We find that such modifications can lead to observational signatures on the cosmic microwave background (CMB) anisotropy spectrum, and provide a new window to explore the CMB anomalies. In this talk we describe these initial conditions, discuss their consequences on the inflationary power spectrum, and compare our results with data from recent CMB experiments. [Preview Abstract] |
Sunday, April 17, 2016 3:42PM - 3:54PM |
M15.00002: Loop Quantum Cosmology and the CMB Ivan Agullo This talk will provide an up-to-date summary of phenomenological explorations in loop quantum cosmology. The possibility of a quantum gravity origin of the anomalies observed in the cosmic microwave background at large angular scales will be discussed. [Preview Abstract] |
Sunday, April 17, 2016 3:54PM - 4:06PM |
M15.00003: Vertex amplitudes in spin foam loop quantum cosmology David Craig We discuss properties of the vertex expansion for homogeneous, isotropic loop quantum cosmological models sourced by a massless, minimally coupled scalar field, which in this model plays the role of an internal matter ``clock''. We show that the vertex expansion, first written down by Ashtekar, Campiglia and Henderson, must be thought of as a short-time expansion in the sense that the amplitude for volume transitions is constrained both by the order of the expansion and by the elapsed scalar field. To calculate the amplitude for significant volume changes or between large differences in the value of the scalar field requires the expansion be evaluated to very high order. [Preview Abstract] |
Sunday, April 17, 2016 4:06PM - 4:18PM |
M15.00004: Boundedness of curvature invariants and lack of strong singularities in loop quantization of Kantowski-Sachs spacetime SAHIL SAINI, PARAMPREET SINGH The Kantowski-Sachs spacetime is singular in classical General Relativity. Assuming the validity of effective Hamiltonian approach, we examine the behavior of the curvature invariants in loop quantum cosmology. Our results show that classical divergences in curvature invariants are resolved in the sense that they are found to be finite for any finite proper time, given that the pressure is finite. Analysis of the strength of singularities indicates that strong singularities are resolved but weak singularities can occur. These results are in tune with similar resolution of physical singularities in results obtained earlier for loop quantization of isotropic and Bianchi-I spacetimes. [Preview Abstract] |
Sunday, April 17, 2016 4:18PM - 4:30PM |
M15.00005: Hysteresis in Loop Quantum Cosmology John Dupuy, Parampreet Singh Hysteresis, a common phenomena in electromagnetic materials in the context of condensed matter physics has also been shown to exist in cosmological, bouncing universe scenarios. Cosmological hysteresis is caused by an asymmetry in the equation of state during the expansion and contraction of the universe. We explore such instances in the context of effective loop quantum cosmology of the spatially closed model for both holonomy and connection quantizations. We find some novel features in the quasi-periodic structures resembling beats in the evolution of these universes for different potentials and in presence of a negative cosmological constant. We also compare results with previous investigations on similar models where such fine structures were not found. [Preview Abstract] |
Sunday, April 17, 2016 4:30PM - 4:42PM |
M15.00006: Loop quantization of Schwarzschild interior revisited Parampreet Singh, Alejandro Corichi Several studies of different inequivalent loop quantizations have shown, that there exists no fully satisfactory quantum theory for the Schwarzschild interior. Existing quantizations fail either on dependence on the fiducial structure or on the lack of the classical limit. Here we put forward a novel viewpoint to construct the quantum theory that overcomes all of the known problems of the existing quantizations. It is shown that the quantum gravitational constraint is well defined past the singularity and that its effective dynamics possesses a bounce into an expanding regime. The classical singularity is avoided, and a semiclassical spacetime satisfying vacuum Einstein's equations is recovered on the "other side" of the bounce. We argue that such metric represents the interior region of a white-hole spacetime, but for which the corresponding "white-hole mass" differs from the original black hole mass. We compare the differences in physical implications with other quantizations. [Preview Abstract] |
Sunday, April 17, 2016 4:42PM - 4:54PM |
M15.00007: A Holographic $c$-Theorem for Schrodinger Spacetimes Weishun Zhong, James Liu We prove a $c$-theorem for holographic renormalization group flows in a Schrodinger spacetime that demonstrates that the effective radius $L(r)$ monotonically decreases from the UV to the IR, where $r$ is the bulk radial coordinate. This result assumes that the bulk matter satisfies the null energy condition, but holds regardless of the value of the critical exponent $z$. We also construct several numerical examples in a model where the Schrodinger background is realized by a massive vector coupled to a real scalar. The full Schrodinger group is realized when $z=2$, and in this case it is possible to construct solutions with constant effective $z(r)=2$ along the entire flow. [Preview Abstract] |
Sunday, April 17, 2016 4:54PM - 5:06PM |
M15.00008: Quantum singularity structure of a class of continuously self-similar spacetimes Deborah Konkowski, Thomas Helliwell, Jon Wiliams The dynamical, classical timelike singularity in a class of continuously self-similar, conformally-static, spherically-symmetric, power-law spacetimes is probed using massless scalar test fields. Ranges of metric parameters for which these classical singularities may be resolved quantum mechanically are determined; however, the wave operator is shown to be not essentially self-adjoint using Weylâ€™s limit point-limit circle criterion. Thus, unfortunately, in this class of spacetimes the wave packet evolution still has the usual ambiguity associated with scattering off singularities. These spacetimes are not healed quantum mechanically. [Preview Abstract] |
Sunday, April 17, 2016 5:06PM - 5:18PM |
M15.00009: Some Implications of a Scale-Invariant Model of Statistical Mechanics to Classical and Black Hole Thermodynamics. Siavash Sohrab A scale-invariant model of statistical mechanics is applied to described modified forms of four laws of classical thermodynamics. Following de Broglie formula $\lambda_{rk} =h/m_{k} v_{rk} $, frequency of matter waves is defined as $\nu_{rk} =k/m_{k} v_{rk} $ leading to stochastic definitions of (Planck, Boltzmann) universal constants ($h=m_{k} <\lambda_{rk} >c$, $k=m_{k} <\nu_{rk} >c)$, $\lambda_{rk} \nu_{rk} =c$, relating to spatiotemporal \textit{Casimir} vacuum fluctuations. Invariant Mach number $Ma_{\beta } =v/v_{r\beta } $ is introduced leading to hierarchy of ``supersonic'' flow separated by shock front, viewed as ``event-horizon'' EH$_{\beta }$, from subsonic flow that terminates at surface of stagnant condensate of ``atoms'' defined as ``black-hole'' BH$_{\beta }$ at scale $\beta $ thus resulting in hierarchy of embedded ``black holes'' at molecular- atomic-, electron-, photon-, tachyon-. . . scales, ad infinitum. Classical black hole will correspond to solid phase photon or \textit{solid-light}. It is argued that Bardeen-Carter-Hawking$^{\, }$(1973) first law of black hole mechanics $\delta M=(\kappa /8\pi )\delta A+\Omega_{H} \delta J+\Phi_{H} \delta Q$, instead of $dE=TdS-PdV$ suggested by Bekenstein (1973), is analogous to first law of thermodynamics expressed as $TdS=PdV+dE$ such that entropy of black hole, rather than to its horizon surface area, will be related to its total energy hence enthalpy $H=TS\mbox{\, }$leading to $S_{BH} =4kN$ in exact agreement with prediction of Major and Setter$^{,\, }$\textit{Class. Quant. Grav.} \textbf{18}(2-3), 5125 (2001). [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2021 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
1 Research Road, Ridge, NY 11961-2701
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700