Instantaneous interaction in massive gravity

Bebronne, M.

doi:10.1016/j.physletb.2008.09.008

Cited by 6 publications

(5 citation statements)

References 30 publications

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“…Note, however, that the instantaneous part of the signal builds up gradually starting from zero at t = 0 and the maximum amplitude that is reached by the time t = |x|/c χ decreases with the distance as 1/|x| 2 . This is similar to the situation in Lorentz violating massive electrodynamics [28,29] and massive gravity [24,30]. It is worth stressing that due to the existence of a preferred frame the instantaneous propagation of signals does not lead to any inconsistencies.…”

Section: The Khronometric Model and Instantaneous Modessupporting

confidence: 71%

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Hořava gravity versus thermodynamics: The black hole case

2011

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Under broad assumptions breaking of Lorentz invariance in gravitational theories leads to tension with unitarity because it allows for processes that apparently violate the second law of thermodynamics. The crucial ingredient of this argument is the existence of black hole solutions with the interior shielded from infinity by a causal horizon. We study how the paradox can be resolved in the healthy extension of Hořava gravity. To this aim we analyze classical solutions describing large black holes in this theory with the emphasis on their causal structure. The notion of causality is subtle in this theory due to the presence of instantaneous interactions. Despite this fact, we find that within exact spherical symmetry a black hole solution contains a space-time region causally disconnected from infinity by a surface of finite area -the 'universal horizon'.We then consider small perturbations of arbitrary angular dependence in the black hole background. We argue that aspherical perturbations destabilize the universal horizon and, at non-linear level, turn it into a finite-area singularity. The causal structure of the region outside the singularity is trivial. If the higher-derivative terms in the equations of motion smear the singularity while preserving the trivial causal structure of the solutions, the thermodynamics paradox would be obviated. As a byproduct of our analysis we prove that the black holes do not have any non-standard long-range hair. We also comment on the relation with Einstein-aether theory, where the solutions with universal horizon appear to be stable.

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Section: The Khronometric Model and Instantaneous Modessupporting

confidence: 71%

“…12 Another derivation of the equivalence between (24) and (30) in the spherically symmetric case, which is also applicable for non-static configuration, is presented in [11]. However, it is based on the assumption that all leaves of the constant khronon field that foliate the space-time are regular and simply connected.…”

Section: Solutionsmentioning

confidence: 99%

Hořava gravity versus thermodynamics: The black hole case

2011

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“…Models described by the action (2.1) with the function F = F Z ij have been studied more intensively [18,21,30]. In particular, it has been shown that for −1 < γ < 0 and for γ = 1 the cosmological perturbations in these models behave identically to those in GR [21].…”

Section: The Massive Gravity Modelmentioning

confidence: 99%

Black hole solutions in massive gravity

Bebronne¹,

Tinyakov²

2009

J. High Energy Phys.

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The static vacuum spherically symmetric solutions in massive gravity are obtained both analytically and numerically. The solutions depend on two parameters (integration constants): the mass M (or, equivalently, the Schwarzschild radius), and an additional parameter, the "scalar charge" S. At zero value of S and positive mass the standard Schwarzschild black hole solutions are recovered. Depending on the parameters of the model and the signs of M and S, the solutions may or may not have horizon. Those with the horizon describe modified black holes provided they are stable against small perturbations. In the analytically solvable example, the modified black hole solutions may have both attractive and repulsive (anti-gravitating) behavior at large distances. At intermediate distances the gravitational potential of a modified black hole may mimics the presence of dark matter. Modified black hole solutions are also found numerically in more realistic massive gravity models which are attractors of the cosmological evolution.

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“…This factor may cancel out in some special cases when the sources contain sufficient number of spatial derivatives, but not in general. Appearance of instantaneous interactions is a common feature of modified gravity models (more generally, gauge theories) with broken Lorentz invariance [20,[54][55][56]. In a theory that does not aspire to a Lorentz invariant UV completion this does not pose an obvious obstruction.…”

Section: Velocity-dependent Forces and Instantaneous Interactionmentioning

confidence: 99%

Models of non-relativistic quantum gravity: the good, the bad and the healthy

Blas

Pujolàs

Sibiryakov

2011

J. High Energ. Phys.

331

472

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Hořava's proposal for non-relativistic quantum gravity introduces a preferred time foliation of space-time which violates the local Lorentz invariance. The foliation is encoded in a dynamical scalar field which we call 'khronon'. The dynamics of the khronon field is sensitive to the symmetries and other details of the particular implementations of the proposal. In this paper we examine several consistency issues present in three non-relativistic gravity theories: Hořava's projectable theory, the healthy non-projectable extension, and a new extension related to ghost condensation. We find that the only model which is free from instabilities and strong coupling is the non-projectable one. We elaborate on the phenomenology of the latter model including a discussion of the couplings of the khronon to matter. In particular, we obtain the parameters of the post-Newtonian expansion in this model and show that they are compatible with current observations.

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Instantaneous interaction in massive gravity

Cited by 6 publications

References 30 publications

Hořava gravity versus thermodynamics: The black hole case

Hořava gravity versus thermodynamics: The black hole case

Black hole solutions in massive gravity

Models of non-relativistic quantum gravity: the good, the bad and the healthy

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