Causal hierarchy in modified gravity

Carballo-Rubio, Raúl; Filippo, Francesco Di; Liberati, Stefano; Visser, Matt

doi:10.1007/jhep12(2020)055

Cited by 9 publications

(11 citation statements)

References 67 publications

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“…[43]) in non-relativistic JHEP04(2021)255 settings, as well as the generalization to space-times with universal horizons of the theorems concerning vacuum state regularity in globally hyperbolic space-times [47,49,50]. Let us stress that such generalizations are far from clear in the quite contrived causality structure of such geometries [51] and that the possibility to fully characterize the vacuum state is not guaranteed due to the peculiar nature of universal horizons that make them similar to Cauchy horizon in non-relativistic frameworks [10,51]. 14 We hope to be able to tackle these issues and more in forthcoming investigations.…”

Section: Discussionmentioning

confidence: 99%

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Hawking radiation from universal horizons

Herrero-Valea

Liberati

Santos-Garcia

2021

J. High Energ. Phys.

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The persistence of a suitable notion of black hole thermodynamics in Lorentz breaking theories of gravity is not only a non-trivial consistency test for such theories, it is also an interesting investigation per se, as it might help us identifying the crucial features at the root of these surprising laws governing such purely gravitational objects. In past investigations, controversial findings were presented in this sense. With the aim of settling this issue, we present here two complementary derivations of Hawking radiation in geometries endowed with universal horizons: a novel feature of back holes in Lorentz breaking theories of gravity which reproduces several properties normally characterizing Killing horizons. We find that both the derivations agree on the fact that the Hawking temperature associated to these geometries is set by the generalized universal horizon peeling surface gravity, as required for consistency with extant derivations of the first law of thermodynamics for these black holes. We shall also comment on the compatibility of our results with previous alternative derivations and on their significance for the survival of the generalized second law of black hole thermodynamics in Lorentz breaking theories of gravity.

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Section: Discussionmentioning

confidence: 99%

“…However, after the formation of a universal horizon, in order to set up a well-defined Cauchy problem, one needs new extra "initial data" (corresponding to some regularity condition at future timelike infinity i + ). See e.g [51]. for a more detailed discussion.…”

mentioning

confidence: 99%

Hawking radiation from universal horizons

Herrero-Valea

Liberati

Santos-Garcia

2021

J. High Energ. Phys.

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“…The study of the causal structure of modified gravity theories [36] shows that one must distinguish between frameworks in which all propagating modes have finite signal velocities and frameworks in which at least one propagating mode has an infinite signal velocity. Following the notation in reference [36], we will refer to these two frameworks as Einsteinaether and Hořava-like, respectively. We start by analyzing the former framework which, since all its signal velocities are finite, is closer to general relativity.…”

Section: Trapping Horizons and Modified Dispersion Relationsmentioning

confidence: 99%

Geodesically complete black holes in Lorentz-violating gravity

Carballo-Rubio

Filippo

Liberati

et al. 2022

J. High Energ. Phys.

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We present a systematic study of the geometric structure of non-singular spacetimes describing black holes in Lorentz-violating gravity. We start with a review of the definition of trapping horizons, and the associated notions of trapped and marginally trapped surfaces, and then study their significance in frameworks with modified dispersion relations. This leads us to introduce the notion of universally marginally trapped surfaces, as the direct generalization of marginally trapped surfaces for frameworks with infinite signal velocities (Hořava-like frameworks), which then allows us to define universal trapping horizons. We find that trapped surfaces cannot be generalized in the same way, and discuss in detail why this does not prevent using universal trapping horizons to define black holes in Hořava-like frameworks. We then explore the interplay between the kinematical part of Penrose’s singularity theorem, which implies the existence of incomplete null geodesics in the presence of a focusing point, and the existence of multiple different metrics. This allows us to present a complete classification of all possible geometries that neither display incomplete physical trajectories nor curvature singularities. Our main result is that not all classes that exist in frameworks in which all signal velocities are realized in Hořava-like frameworks. However, the taxonomy of geodesically complete black holes in Hořava-like frameworks includes diverse scenarios such as evaporating regular black holes, regular black holes bouncing into regular white holes, and hidden wormholes.

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“…The study of the causal structure of modified gravity theories [38] shows that one must distinguish between frameworks in which all propagating modes have finite signal velocities and frameworks in which at least one propagating mode has an infinite signal velocity. Following the notation in reference [38], we will refer to these two frameworks as Einsteinaether and Hořava-like, respectively. We start by analyzing the former framework which, since all its signal velocities are finite, is closer to general relativity.…”

Section: Trapping Horizons and Modified Dispersion Relationsmentioning

confidence: 99%

“…Note that N = N (τ, ) has been defined implicitly in Eqs. (37) and (38). The associated null vectors {k, l} are proportional to…”

Section: Specific Coordinatesmentioning

confidence: 99%

Geodesically complete black holes in Lorentz-violating gravity

Carballo-Rubio,

Di Filippo,

Liberati

et al. 2021

Preprint

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We present a systematic study of the geometric structure of non-singular spacetimes describing black holes in Lorentz-violating gravity. We start with a review of the definition of trapping horizons, and the associated notions of trapped and marginally trapped surfaces, and then study their significance in frameworks with modified dispersion relations. This leads us to introduce the notion of universally marginally trapped surfaces, as the direct generalization of marginally trapped surfaces for frameworks with infinite signal velocities (Hořava-like frameworks), which then allows us to define universal trapping horizons. We find that trapped surfaces cannot be generalized in the same way, and discuss in detail why this does not prevent using universal trapping horizons to define black holes in Hořava-like frameworks. We then explore the interplay between the kinematical part of Penrose's singularity theorem, which implies the existence of incomplete null geodesics in the presence of a focusing point, and the existence of multiple different metrics. This allows us to present a complete classification of all possible geometries that neither display incomplete physical trajectories nor curvature singularities. Our main result is that not all classes that exist in frameworks in which all signal velocities are realized in Hořava-like frameworks. However, the taxonomy of geodesically complete black holes in Hořava-like frameworks includes diverse scenarios such as evaporating regular black holes, regular black holes bouncing into regular white holes, and hidden wormholes.

show abstract

Causal hierarchy in modified gravity

Cited by 9 publications

References 67 publications

Hawking radiation from universal horizons

Hawking radiation from universal horizons

Geodesically complete black holes in Lorentz-violating gravity

Geodesically complete black holes in Lorentz-violating gravity

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