Horizon entropy with loop quantum gravity methods

Pranzetti, Daniele; Sahlmann, Hanno

doi:10.1016/j.physletb.2015.04.070

Cited by 26 publications

(16 citation statements)

References 60 publications

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“…It was also shown in [45] how the self dual formulation allows to recover naturally the thermal character of the near-horizon radiation. Additional results have been obtained in this context, reinforcing the status of the self dual variables as well suited to capture the right semi-classical result in the context of black hole thermodynamics in LQG [46][47][48][49]. See also [50][51][52][53] for related investigations in different contexts.…”

Section: Why Use Self-dual Ashtekar Variables?supporting

confidence: 55%

Covariance in self-dual inhomogeneous models of effective quantum geometry: Spherical symmetry and Gowdy systems

Achour¹,

Brahma

2018

Phys. Rev. D

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When applying the techniques of Loop Quantum Gravity (LQG) to symmetry-reduced gravitational systems, one first regularizes the scalar constraint using holonomy corrections, prior to quantization. In inhomogeneous system, where a residual spatial diffeomorphism symmetry survives, such modification of the gauge generator generating time reparametrization can potentially lead to deformations or anomalies in the modified algebra of first class constraints. When working with self-dual variables, it has already been shown that, for spherically symmetric geometry coupled to a scalar field, the holonomy-modified constraints do not generate any modifications to general covariance, as one faces in the real variables formulation, and can thus accommodate local degrees of freedom in such inhomogeneous models. In this paper, we extend this result to Gowdy cosmologies in the self-dual Ashtekar formulation. Furthermore, we show that the introduction of aμ−scheme in midisuperspace models, as is required in the 'improved dynamics' of LQG, is possible in the self-dual formalism while being out of reach in the current effective models suing real-valued Ashtekar-Barbero variables.Our results indicate the advantages of using the self-dual variables to obtain a covariant loop regularization prior to quantization in inhomogeneous symmetry reduced polymer models, implementing additionally the crucialμ-scheme, and thus a consistent semiclassical limit. 2

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Section: Why Use Self-dual Ashtekar Variables?supporting

confidence: 55%

Covariance in self-dual inhomogeneous models of effective quantum geometry: Spherical symmetry and Gowdy systems

Achour¹,

Brahma

2018

Phys. Rev. D

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“…It seems natural to expect these magnetic edge modes to be encoded in a boundary connection field. Either by providing with a Chern-Simons-like boundary symplectic term [28][29][30] or with a mixed term coupling the boundary connection to the boundary frame field [31] as was derived in the case of isolated horizon boundary conditions.…”

Section: Discussionmentioning

confidence: 99%

Kinematical gravitational charge algebra

Freidel¹,

Livine²,

Pranzetti³

2020

Phys. Rev. D

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When formulated in terms of connection and co-frames, and in the time gauge, the phase space of general relativity consists of a pair of conjugate fields: the flux 2-form and the Ashtekar connection. On this phase-space, one has to impose the Gauss constraints, the vector, and scalar Hamiltonian constraints. These are respectively generating local SU(2) gauge transformations, spatial diffeomorphisms, and time diffeomorphisms. We write the Gauss and space diffeomorphism constraints as conservation laws for a set of boundary charges, representing spin and momenta, respectively. We prove that these kinematical charges generate a local Poincaré ISU(2) symmetry algebra. This gives strong support to the recent proposal of Poincaré charge networks as a new realm for discretized general relativity [1]. *

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“…Even though all these expressions have been presented for completeness, for our later purposes we will use the expression dependent on contorsion tensor as given by Eq. (22). This will help to simplify the algebra significantly.…”

Section: Noether Current In Presence Of Spacetime Torsionmentioning

confidence: 99%

Noether current, black hole entropy and spacetime torsion

Chakraborty

Dey

2018

Physics Letters B

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We show that the presence of spacetime torsion, unlike any other non-trivial modifications of the Einstein gravity, does not affect black hole entropy. The theory being diffeomorphism invariant leads to a Noether current and hence to a Noether charge, which can be associated to the heat content of the spacetime. Furthermore, the evolution of the spacetime inheriting torsion can be encoded in the difference between suitably defined surface and bulk degrees of freedom. For static spacetimes the surface and bulk degrees of freedom coincides, leading to holographic equipartition. In doing so one can see that the surface degrees of freedom originate from horizon area and it is clear that spacetime torsion never contributes to the surface degrees of freedom and hence neither to the black hole entropy. We further show that the gravitational Hamiltonian in presence of torsion does not inherit any torsion dependence in the boundary term and hence the first law originating from the variation of the Hamiltonian, relates entropy to area. This reconfirms our claim that torsion does not modify the black hole entropy. *

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Horizon entropy with loop quantum gravity methods

Cited by 26 publications

References 60 publications

Covariance in self-dual inhomogeneous models of effective quantum geometry: Spherical symmetry and Gowdy systems

Covariance in self-dual inhomogeneous models of effective quantum geometry: Spherical symmetry and Gowdy systems

Kinematical gravitational charge algebra

Noether current, black hole entropy and spacetime torsion

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