- 24,753
- 794
http://arxiv.org/abs/1504.05352
Black hole spectroscopy from Loop Quantum Gravity models
Aurelien Barrau, Xiangyu Cao, Karim Noui, Alejandro Perez
(Submitted on 21 Apr 2015)
Using Monte Carlo simulations, we compute the integrated emission spectra of black holes in the framework of Loop Quantum Gravity (LQG). The black hole emission rates are governed by the entropy whose value, in recent holographic loop quantum gravity models, was shown to agree at leading order with the Bekenstein-Hawking entropy. Quantum corrections depend on the Barbero-Immirzi parameter γ. Starting with black holes of initial horizon area A∼102 in Planck units, we present the spectra for different values of γ. Each spectrum clearly decomposes in two distinct parts: a continuous background which corresponds to the semi-classical stages of the evaporation and a series of discrete peaks which constitutes a signature of the deep quantum structure of the black hole. We show that γ has an effect on both parts that we analyze in details. Finally, we estimate the number of black holes and the instrumental resolution required to experimentally distinguish between the considered models.
11 pages, 9 figures
http://arxiv.org/abs/1503.08640
New first order Lagrangian for General Relativity
Yannick Herfray, Kirill Krasnov
(Submitted on 30 Mar 2015)
We describe a new BF-type first-order in derivatives Lagrangian for General Relativity. The Lagrangian depends on a connection field as well as a Lie-algebra valued two-form field, with no other fields present. There are two free parameters, which translate into the cosmological constant and the coefficient in front of a topological term. When one of the parameters is set to zero, the theory becomes topological. When the other parameter is zero, the theory reduces to the (anti-) self-dual gravity. Thus, our new Lagrangian interpolates between the topological and anti-self-dual gravities. It also interprets GR as the (anti-) self-dual gravity with an extra quadratic in the auxiliary two-form field term added to the Lagrangian, precisely paralleling the situation in Yang-Mills theory.
4 pages
possibly of general interest:
http://arxiv.org/abs/1412.8462
An operational approach to spacetime symmetries: Lorentz transformations from quantum communication
Philipp A. Hoehn, Markus P. Mueller
(Submitted on 29 Dec 2014 (v1), last revised 23 Apr 2015 (this version, v2))
In most approaches to fundamental physics, spacetime symmetries are postulated a priori and then explicitly implemented in the theory. This includes Lorentz covariance in quantum field theory and diffeomorphism invariance in quantum gravity, which are seen as fundamental principles to which the final theory has to be adjusted. In this paper, we suggest, within a much simpler setting, that this kind of reasoning can actually be reversed, by taking an operational approach inspired by quantum information theory. We consider observers in distant laboratories, with local physics described by the laws of abstract quantum theory, and without presupposing a particular spacetime structure. We ask what information-theoretic effort the observers have to spend to synchronize their descriptions of local physics. If there are "enough" observables that can be measured jointly on different types of systems, we show that the observers' descriptions are related by an element of the orthochronous Lorentz group O^+(3,1), together with a global scaling factor. This operational derivation of the Lorentz transformations correctly describes the physics of relativistic Stern-Gerlach measurements in the WKB approximation, and predicts representations of different spin and Wigner little groups. This result also hints at a novel information-theoretic perspective on spacetime.
Comments: 37 pages, 6 figures, added two new sections, additional explanations and motivations, updated references, corrected typos
Black hole spectroscopy from Loop Quantum Gravity models
Aurelien Barrau, Xiangyu Cao, Karim Noui, Alejandro Perez
(Submitted on 21 Apr 2015)
Using Monte Carlo simulations, we compute the integrated emission spectra of black holes in the framework of Loop Quantum Gravity (LQG). The black hole emission rates are governed by the entropy whose value, in recent holographic loop quantum gravity models, was shown to agree at leading order with the Bekenstein-Hawking entropy. Quantum corrections depend on the Barbero-Immirzi parameter γ. Starting with black holes of initial horizon area A∼102 in Planck units, we present the spectra for different values of γ. Each spectrum clearly decomposes in two distinct parts: a continuous background which corresponds to the semi-classical stages of the evaporation and a series of discrete peaks which constitutes a signature of the deep quantum structure of the black hole. We show that γ has an effect on both parts that we analyze in details. Finally, we estimate the number of black holes and the instrumental resolution required to experimentally distinguish between the considered models.
11 pages, 9 figures
http://arxiv.org/abs/1503.08640
New first order Lagrangian for General Relativity
Yannick Herfray, Kirill Krasnov
(Submitted on 30 Mar 2015)
We describe a new BF-type first-order in derivatives Lagrangian for General Relativity. The Lagrangian depends on a connection field as well as a Lie-algebra valued two-form field, with no other fields present. There are two free parameters, which translate into the cosmological constant and the coefficient in front of a topological term. When one of the parameters is set to zero, the theory becomes topological. When the other parameter is zero, the theory reduces to the (anti-) self-dual gravity. Thus, our new Lagrangian interpolates between the topological and anti-self-dual gravities. It also interprets GR as the (anti-) self-dual gravity with an extra quadratic in the auxiliary two-form field term added to the Lagrangian, precisely paralleling the situation in Yang-Mills theory.
4 pages
possibly of general interest:
http://arxiv.org/abs/1412.8462
An operational approach to spacetime symmetries: Lorentz transformations from quantum communication
Philipp A. Hoehn, Markus P. Mueller
(Submitted on 29 Dec 2014 (v1), last revised 23 Apr 2015 (this version, v2))
In most approaches to fundamental physics, spacetime symmetries are postulated a priori and then explicitly implemented in the theory. This includes Lorentz covariance in quantum field theory and diffeomorphism invariance in quantum gravity, which are seen as fundamental principles to which the final theory has to be adjusted. In this paper, we suggest, within a much simpler setting, that this kind of reasoning can actually be reversed, by taking an operational approach inspired by quantum information theory. We consider observers in distant laboratories, with local physics described by the laws of abstract quantum theory, and without presupposing a particular spacetime structure. We ask what information-theoretic effort the observers have to spend to synchronize their descriptions of local physics. If there are "enough" observables that can be measured jointly on different types of systems, we show that the observers' descriptions are related by an element of the orthochronous Lorentz group O^+(3,1), together with a global scaling factor. This operational derivation of the Lorentz transformations correctly describes the physics of relativistic Stern-Gerlach measurements in the WKB approximation, and predicts representations of different spin and Wigner little groups. This result also hints at a novel information-theoretic perspective on spacetime.
Comments: 37 pages, 6 figures, added two new sections, additional explanations and motivations, updated references, corrected typos
Last edited: