Viscosity Bound and Causality Violation

Brigante, Mauro; Liu, Hong; Myers, Robert C.; Shenker, Stephen H.; Yaida, Sho

doi:10.1103/physrevlett.100.191601

Cited by 445 publications

(612 citation statements)

References 37 publications

(48 reference statements)

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“…This scale does not show up in our calculations because we have considered perturbations of maximally symmetric backgrounds where the perturbation operator (2.7) is simply a constant multiple of the Einstein perturbation operator. This is no longer the case when the background has a non-trivial Weyl tensor, as in the case of the planar black hole calculation of [39].…”

Section: Discussionmentioning

confidence: 99%

“…A third pathology was recently identified on the Einstein branch, through calculations of the viscosity-entropy bound [39] for gauge theories with a Gauss-Bonnet gravity dual. In the background of an EGB planar black hole, it was found that graviton wave packets can propagate with superluminal speeds whenever 9 25 ≤ 8αk 2 ≤ 1, where 1/k is the AdS length.…”

Section: Discussionmentioning

confidence: 99%

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The instability of vacua in Gauss-Bonnet gravity

Charmousis

Padilla

2008

J. High Energy Phys.

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Owing to the quadratic nature of the theory, Einstein-Gauss-Bonnet gravity generically permits two distinct vacuum solutions. One solution (the "Einstein" vacuum) has a well defined limit as the Gauss-Bonnet coupling goes to zero, whereas the other solution (the "stringy" vacuum) does not. There has been some debate regarding the stability of these vacua, most recently from Deser & Tekin who have argued that the corresponding black hole solutions have positive mass and as such both vacua are stable. Whilst the statement about the mass is correct, we argue that the stringy vacuum is still perturbatively unstable. Simply put, the stringy vacuum suffers from a ghost-like instability that is not excited by the spherically symmetric black hole, but would be excited by any source likely to emit gravitational waves, such as a binary system. This result is reliable except in the strongly coupled regime close to the Chern-Simons limit, when the two vacua are almost degenerate. In this regime, we study instanton transitions between branches via bubble nucleation, and calculate the nucleation probability. This demonstrates that there is large mixing between the vacua, so that neither of them can accurately describe the true quantum vacuum. We also present a new gravitational instanton describing black hole pair production in de Sitter space on the Einstein branch, which is preferred to the usual Nariai instantons and is not present in pure Einstein gravity.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The instability of vacua in Gauss-Bonnet gravity

Charmousis

Padilla

2008

J. High Energy Phys.

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“…In the context of Lovelock theory, this case has received attention since it's the simplest case that admits a unique constant curvature solution that also propagates a graviton [47][48][49]. The theory therefore reads 5) and the black holes solution reduces to…”

Section: Pure Quasi-topological Gravitymentioning

confidence: 99%

“…KSS bound [3] (see [4] and [5]). Lovelock theories provide one with a setup where certain control at a computational level can be attained.…”

Section: Jhep04(2017)066mentioning

confidence: 99%

Quintic quasi-topological gravity

Cisterna

Guajardo

Hassaı̈ne

et al. 2017

J. High Energ. Phys.

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We construct a quintic quasi-topological gravity in five dimensions, i.e. a theory with a Lagrangian containing R 5 terms and whose field equations are of second order on spherically (hyperbolic or planar) symmetric spacetimes. These theories have recently received attention since when formulated on asymptotically AdS spacetimes might provide for gravity duals of a broad class of CFTs. For simplicity we focus on five dimensions. We show that this theory fulfils a Birkhoff's Theorem as it is the case in Lovelock gravity and therefore, for generic values of the couplings, there is no s-wave propagating mode. We prove that the spherically symmetric solution is determined by a quintic algebraic polynomial equation which resembles Wheeler's polynomial of Lovelock gravity. For the black hole solutions we compute the temperature, mass and entropy and show that the first law of black holes thermodynamics is fulfilled. Besides of being of fourth order in general, we show that the field equations, when linearized around AdS are of second order, and therefore the theory does not propagate ghosts around this background. Besides the class of theories originally introduced in arXiv:1003.4773, the general geometric structure of these Lagrangians remains an open problem.

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“…Only with the higher derivative corrections [71][72][73] or in a anisotropic gravity background [74][75][76][77] one can get deviation from 1 4π . In order to introduce temperature dependence behavior of η/s, we will follow the formalism in [78][79][80] and continue our studies in [65].…”

Section: Jhep06(2015)046mentioning

confidence: 99%

Temperature dependent transport coefficients in a dynamical holographic QCD model

Huang

2015

J. High Energ. Phys.

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Abstract:We investigate temperature dependent behavior of various transport coefficients in a dynamical holographical QCD model. We show the nontrivial temperature dependent behavior of the transport coefficients, like bulk viscosity, electric conductivity as well as jet quenching parameter, and it is found that all these quantities reveal information of the phase transition. Furthermore, with introducing higher derivative corrections in 5D gravity, the shear viscosity over entropy density ratio also shows a valley around phase transition, and it is found that the shear viscosity over entropy density ratio times the jet quenching over temperature cubic ratio almost remains as a constant above phase transition, and the value is two times larger than the perturbative result in Phys.Rev. Lett.99.192301(2007).

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Viscosity Bound and Causality Violation

Cited by 445 publications

References 37 publications

The instability of vacua in Gauss-Bonnet gravity

The instability of vacua in Gauss-Bonnet gravity

Quintic quasi-topological gravity

Temperature dependent transport coefficients in a dynamical holographic QCD model

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