Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session H11: Thermodynamic and Mathematical Aspects of Gravity |
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Sponsoring Units: DGRAV Chair: David Garfinkle, Oakland University Room: Sheraton Governor's Square 17 |
Sunday, April 14, 2019 10:45AM - 10:57AM |
H11.00001: Thermodynamic equivalence of Jordan and Einstein frame in scalar-tensor theory Krishnakanta Bhattacharya Among the various modified theories of gravity, the scalar-tensor theory is one of the most post popular one and one of the most studied as well. This theory is described in the two frames– the Jordan frame and the Einstein frame. Although, the theory is successful in various avenues, there are two major controversies in the theory itself. These are– (1) Whether the conformal equivalence of the action in the two frames is merely a mathematical equivalence or whether these two frames are indeed equivalent. (2) What are the explicit covariant expressions of the physical quantities (energy, entropy, temperature) and how they are connected in the two frames. Although, the expression of the entropy and the temperature is widely accepted to some extent but, there is a controversy in the expression of the energy which can be used for the thermodynamic description in this theory. We in Phys. Rev. D 95, no. 6, 064026 (2017) and Phys. Rev. D 97, no. 12, 124013 (2018) have explored these issues. We show that by properly defining the Lagrangians in the two frames, one can obtain the first law and the covariant expressions of the thermodynamic parameters (including energy) following the Iyer-Wald formalism. We also show that all the thermodynamic parameters are |
Sunday, April 14, 2019 10:57AM - 11:09AM |
H11.00002: Gedanken Experiments to Destroy a BTZ Black Hole Baoyi Chen, Feng-Li Lin, Bo Ning We consider Wald's type of gedanken experiments to destroy an extremal or near-extremal BTZ black hole in 3-dimensional torsional Mielke-Barkler gravity by throwing matter into the horizon. Provided the null energy condition for the falling matter, we prove the following—( i ) in MB model, an extremal BTZ black hole can be overspun and becomes a naked conical singularity, as long as the coupling coefficients in the theory live in a certain region of the parameter space; ( ii ) in 3-dimensional Einstein gravity and chiral gravity, which are two special limits of MB model , an extremal BTZ black hole cannot be overspun; and ( iii ) in both Einstein gravity and chiral gravity, a near-extremal BTZ black hole cannot be overspun, thus weak cosmic censorship is preserved. Wald's type of gedanken experiment provides an operational procedure of proving the third law of black hole mechanics. Through the AdS/CFT correspondence, our results on BTZ black holes also indicate that a third law of thermodynamics holds for the holographic CFTs dual to 3-dimensional Einstein gravity and chiral gravity. |
Sunday, April 14, 2019 11:09AM - 11:21AM |
H11.00003: An Entropy-Area Law for Neutron Stars Near the Black Hole Threshold Stephon Alexander, Kent Yagi, Nicolas Yunes Neutron stars have been shown to exhibit a set of universal relations independent of their equation of state that bears semblance to the black hole no hair relations. In this talk, I will show that a rescaled entropy measure also possesses nearly universal behavior for an equilibrium sequence of isolated neutron stars constructed numerically. Moreover, as the stellar compactness (or central density) in the sequence is increased, the degree of universality increases, the entropy approaches the black hole limit, and the entropy scales more and more with the stellar surface area instead of the stellar volume. All of these results point strongly to the existence of an entropy-area law for neutron stars near the threshold of gravitational collapse. |
Sunday, April 14, 2019 11:21AM - 11:33AM |
H11.00004: Space-time approach to locomotion in deformable environments Pablo Laguna, Shengkai Li, Jennifer Rieser, Daniel Goldman While most studies of locomotion treat the environment and the locomotor separately, there exist a class of self-propelled systems which change the environment so dramatically that a treatment of them as a single entity is more natural. We study the dynamics of a robophysical car driving around a central depression in a deformable membrane. Inspired by its observed orbits, which mimic dynamics in general relativistic systems, we recast the propulsion problem as geodesics of a test particle in a fiducial space-time. This view enables us to understand the character of robot dynamics as that of motion in curved space-times, opening the door toward an Einsteinian motivated framework for locomotion in deformable surfaces. |
Sunday, April 14, 2019 11:33AM - 11:45AM |
H11.00005: Perturbing towards gravity: crossing channels in the D1-D5 CFT Benjamin A Burrington, Thomas DeBeer, Ian Jardine, Amanda W. Peet In previous work we explored correlators of bare twists in bosonic orbifold CFT's, which have a universal behavior at large N. We were able to show that this universality comes from an underlying algebraic structure: the crossing channels are accounted for by fractional Virasoro mode excitations of the bare twists. We extend our previous work to the supersymmetric case relevant for the D1-D5 brane intersection, where again certain correlation functions have a universal structure at large N. We show for a set of chiral-primary and anti-chiral-primary fields that the crossing channels are again explained algebraically, this time using a subsector of the superconformal algebra to excite the primary twists. Further, the operator used to deform the CFT towards a gravity limit lies in the tower of fractionally excited primary operators, and so this algebraic approach should be useful when bridging the gap between the gravity and field theory limits. |
Sunday, April 14, 2019 11:45AM - 11:57AM |
H11.00006: Quantum Field Origin of Gravitation DT Froedge Gravitation defined in curved space has never been found to be compatible with quantum mechanics or quantum field theory. This is likely due to the fact that (QM) theory is based in local conservation of energy and the other (GR) defines energy globally, and is not locally conserved [Noether 1]. Equations mixed with variables from two energy conservation laws, could neither be invariant nor covariant under coordinate transformations. This paper presents a theory for a gradient in c induced by QFT equivalent to the gradient in c induced by gravitation. It has been illustrated that for photons, and confined light speed particles, a gradient in c demonstrates the effect of gravitation on the energy equivalent mass. This creates a theoretical mechanism for the origin of gravitation within a Lorenz, local conservation four-space. http://www.arxdtf.org/css/QFTGravitation.pdf |
Sunday, April 14, 2019 11:57AM - 12:09PM |
H11.00007: The speed of light as a dependent cosmological parameter and the gravitational attenuation of distant matter Lance Williams The coincidence between the square of the speed of light, c^{2}, and the Newtonian gravitational potential of the universe, suggests a dependence of the magnitude of c on cosmological parameters. Such a cosmological dependence is obtained by applying standard initial-value considerations of general relativity to the cosmological Robertson-Walker metric. Specifically, the time-time component of the cosmological metric is considered as a variable field on spatial foliations of the cosmological metric. A basic quantification emerges for c^{2} in terms of the gravitational constant G, the cosmological matter density ρ, and the cosmological constant Λ, such that c^{2}∼ ρG/Λ. The Newtonian result obtains from the non-linear elliptic equation for the case of a matter-only universe, but in that case, c is not independently quantified. The cosmological constant plays a crucial role, not only in providing a lengthscale that can be combined with the timescale of ρG to provide a cosmological velocity scale, but also in attenuating the gravitational effect of distant matter compared to a Newtonian calculation. Although variation of the speed of light is implied on cosmological time scales, there is no effect on the Friedmann equation, and conservation of energy is preserved. |
Sunday, April 14, 2019 12:09PM - 12:21PM |
H11.00008: Dark Energy's Role in General Relativity Scott S Gordon The name dark energy was given to the energy responsible for accelerating the contents of the universe “outward”. This energy is being called “dark” until a theory could be found to account for it. The field of physics has been built on the scientific method fostering well-established theories that build on one another. However, so far, no derivations stemming from our current mathematics, expressing our most validated theories, has been able to reveal the nature of “dark” energy. It may be time to consider... What if it is impossible to derive the nature of dark energy using the mathematics expressing our current theories? What if a new model of the universe is required; a more basic model to which math is applied? A model that starts with only one ingredient and its associated energy as the only way to reveal the nature of dark energy? Such a basic elementary model would have to be derived independently from our current complex theories and yet be able to derive our current theories. The new model could then define dark energy and reveal the role dark energy plays in gravity, general relativity, and much more. |
Sunday, April 14, 2019 12:21PM - 12:33PM |
H11.00009: The Temperature Dependence of Gravitation and Unification of Gravitation & Electromagnetism C. Y. Lo According to Newton and Einstein, gravitation is independent of the temperature, but experiments show that the gravitation of a metal is reduced as temperature increases. Thus, it is impossible to obtain the most accurate Newtonian coupling constant with the existing method. Einstein also predicts the unification of gravitation and electromagnetism, but he fails to show this. It will be shown that his two errors have a common reason, his failure to see the existence of the repulsive charge-mass interaction. The root of his errors is due to Einstein’s misconception that, unlike Maxwell, he did not see that unification needs some additional interactions. In addition, Einstein did not see that his formula E = mc^{2} is inconsistent with his field equation. Moreover, the unproven invalid E = mc^{2} is the source of his other errors in his general relativity. Since the charge-mass interaction is absent from quantum theory, Einstein is right that current quantum theory is not final. |
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