Horava gravity versus thermodynamics: The Black hole case
Horava gravity versus thermodynamics: The Black hole case
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DOI：
10.1103/physrevd.84.124043
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发表时间：
2011-10
影响因子：
5
通讯作者：
D. Blas;S. Sibiryakov
中科院分区：
文献类型：
--
作者：
D. Blas;S. Sibiryakov
在广义假设下，引力理论中洛伦兹不变性的破坏导致了与幺正性的张力，因为它允许明显违反热力学第二定律的过程。这一论点的关键要素是存在黑洞解，其内部被因果视界从无穷远处屏蔽。我们研究如何解决的悖论，在健康的霍拉瓦引力的扩展。为了这个目的，我们分析经典的解决方案，在这个理论中描述大黑洞的因果结构的重点。因果关系的概念在这个理论中是微妙的，因为存在瞬时的相互作用。尽管如此，我们发现在精确球对称中，黑洞解包含一个时空区域，该区域通过一个有限面积的表面与无穷大因果地断开--“宇宙视界”。然后我们考虑黑洞背景中任意角度依赖的小扰动。我们认为，非球面扰动不稳定的普遍视界，并在非线性水平上，把它变成一个有限区域的奇点。奇点之外区域的因果结构是平凡的。如果运动方程中的高阶导数项在保持解的平凡因果结构的同时涂抹了奇点，那么热力学悖论就可以消除。作为我们分析的副产品，我们证明了黑洞没有任何非标准的长程毛发。我们还评论了与爱因斯坦以太理论的关系，其中具有普遍视界的解决方案似乎是稳定的。
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 Horava 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 the nonlinear 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 by-product of our analysis we prove that the black holes do not have any nonstandard long-range hair. We also comment on the relation with Einstein-aether theory, where the solutions with a universal horizon appear to be stable.