标题： 洛伦兹破缺引力中的霍金辐射：两个视界的传说 显示英文标题

标题： Hawking Radiation in Lorentz Violating Gravity: A Tale of Two Horizons

摘要： 自从提出以来，引力的洛伦兹破缺理论对黑洞热力学构成了潜在威胁，因为超光速信号似乎与黑洞概念本身不相容。值得注意的是，人们很快意识到，在这些理论中，由于存在普遍视界：即对于任意高速信号的因果障碍，时空中因果不相连的区域仍然可能存在。一些研究，有时结果相反，已经进行以确定这些视界是否可以与类似于广义相对论中Killing视界所关联的健康热力学性质相关联。在本工作中，我们提供了我们认为从这项研究和以前的研究中得出的最终图景。总之，我们展示了以下内容：1）存在一种热辐射，而且最重要的是与物质种类无关，这种辐射由其表面重力决定；2）由于物质场的色散关系被修改，在发射光谱的低能部分受到Killing视界的影响，方式类似于有效折射率，在低能（相对于洛伦兹破缺尺度）下导致一种类似于标准霍金谱的辐射（即由Killing视界表面重力决定的谱）；3）整个图景与全局定义良好的真空态相容，即与首选观测者相关的安鲁态，然而在非常低的能量下，它基本上无法与无度规自由下落观测者相关的标准安鲁真空区分开来。因此可以得出结论，霍金辐射在包含局部洛伦兹不变性破坏的引力理论中也表现出惊人的韧性。 显示英文摘要

摘要： Since their proposal, Lorentz violating theories of gravity have posed a potential threat to black hole thermodynamics, as superluminal signals appeared to be incompatible with the very black hole notion. Remarkably, it was soon realized that in such theories causally disconnected regions of space-time can still exist thanks to the presence of universal horizons: causal barriers for signals of arbitrary high speed. Several investigations, sometimes with contrasting results, have been performed so to determine if these horizons can be associated with healthy thermodynamic properties similar to those associated with Killing horizons in General Relativity. In this work we offer what we deem to be the final picture emerging from this and previous studies. In summary we show that: 1) there is a thermal, and most of all species-independent, emission associated to universal horizons, determined by their surface gravity; 2) due to the modified dispersion relation of the matter fields, the low energy part of the emitted spectrum is affected by the presence of the Killing horizon, in a way similar to an effective refractive index, leading at low energies (w.r.t. the Lorentz breaking scale) to an emission that mimics a standard Hawking spectrum (i.e. one determined by the Killing horizon surface gravity); 3) the whole picture is compatible with a globally well defined vacuum state i.e. an Unruh state associated with preferred observers, which however at very low energies it is basically indistinguishable from the standard Unruh vacuum associated to metric free-falling observers. One can then conclude that Hawking radiation is remarkably resilient even within the context of gravitational theories entailing the breakdown of local Lorentz invariance.