Black-hole horizons in modified spacetime structures arising from canonical quantum gravity

Bojowald, Martin; Paily, George M.; Reyes, Juan D.; Tibrewala, Rakesh

doi:10.1088/0264-9381/28/18/185006

Cited by 18 publications

(61 citation statements)

References 78 publications

(142 reference statements)

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“…The dynamics is therefore modified, which is consistent with the results of several detailed investigations of cosmological [50,51,52,53,54,6,55,56,57] and black-hole consequences [58,4,3,59] in terms of physical, coordinate-independent effects. An open question has been whether one can introduce a modified effective space-time metric which is generally covariant in the standard sense, or whether the deformed algebroid modifies this symmetry and leads to an entirely new space-time structure.…”

Section: Modified Theorysupporting

confidence: 86%

Hypersurface-deformation algebroids and effective spacetime models

et al. 2016

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In canonical gravity, covariance is implemented by brackets of hypersurface-deformation generators forming a Lie algebroid. Lie algebroid morphisms therefore allow one to relate different versions of the brackets that correspond to the same space-time structure. An application to examples of modified brackets found mainly in models of loop quantum gravity can in some cases map the space-time structure back to the classical Riemannian form after a field redefinition. For one type of quantum corrections (holonomies), signature change appears to be a generic feature of effective space-time, and is shown here to be a new quantum space-time phenomenon which cannot be mapped to an equivalent classical structure. In low-curvature regimes, our constructions prove the existence of classical space-time structures assumed elsewhere in models of loop quantum cosmology, but also shows the existence of additional quantum corrections that have not always been included.

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Section: Modified Theorysupporting

confidence: 86%

Hypersurface-deformation algebroids and effective spacetime models

et al. 2016

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“…Interestingly, it was realized in a series of articles [49][50][51][52][53][54] that under suitable conditions, one can construct regularizations where the deformed algebra of constraints remain closed 3 . The consequences of this deformed covariance was then investigated in depth in the context of spherically symmetric backgrounds [60][61][62] and then extended to more general symmetry reduced models in [63][64][65][66][67][68].…”

Section: Introductionmentioning

confidence: 99%

Deformed General Relativity and Quantum Black Holes Interior

2020

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Effective models of black holes interior have led to several proposals for regular black holes. In the so-called polymer models, based on effective deformations of the phase space of spherically symmetric general relativity in vacuum, one considers a deformed Hamiltonian constraint while keeping a non-deformed vectorial constraint, leading under some conditions to a notion of deformed covariance. In this article, we revisit and study further the question of covariance in these deformed gravity models. In particular, we propose a Lagrangian formulation for these deformed gravity models where polymer-like deformations are introduced at the level of the full theory prior to the symmetry reduction and prior to the Legendre transformation. This enables us to test whether the concept of deformed covariance found in spherically symmetric vacuum gravity can be extended to the full theory, and we show that, in the large class of models we are considering, the deformed covariance can not be realized beyond spherical symmetry in the sense that the only deformed theory which leads to a closed constraints algebra is general relativity. Hence, we focus on the spherically symmetric sector, where there exist non-trivial deformed but closed constraints algebras. We investigate the possibility to deform the vectorial constraint as well and we prove that non-trivial deformations of the vectorial constraint with the condition that the constraints algebra remains closed do not exist. Then, we compute the most general deformed Hamiltonian constraint which admits a closed constraints algebra and thus leads to a well-defined effective theory associated with a notion of deformed covariance. Finally, we study static solutions of these effective theories and, remarkably, we solve explicitly and in full generality the corresponding modified Einstein equations, even for the effective theories which do not satisfy the closeness condition. In particular, we give the expressions of the components of the effective metric (for static and spherically symmetric black holes interior) in terms of the functions that govern the deformations of the theory.

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“…The anomaly freedom of the (polarized) Gowdy system was treated in [17]. Besides investigating the covariance of these models, effective black holes metrics for the quantum corrected Schwarzschild and Reissner Nordstrom black hole, and for the LTB space-time, were derived in [13,[18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

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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Black-hole horizons in modified spacetime structures arising from canonical quantum gravity

Cited by 18 publications

References 78 publications

Hypersurface-deformation algebroids and effective spacetime models

Hypersurface-deformation algebroids and effective spacetime models

Deformed General Relativity and Quantum Black Holes Interior

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

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