空灵主题变奏曲
Variations on an aethereal theme
摘要：
我们考虑一类洛伦兹破坏的引力理论，涉及一个类时单位向量场（以太）耦合到一个度规，两个例子是爱因斯坦以太理论和Hoenavava引力。作用总是包括度量的里奇标量和以太协变导数的二次不变量，但理论的不同之处在于以太是如何从其他场构造的，以及这些场是否在作用中变化。不变化的域定义了打破非对称不变性的背景结构，包括线程、折叠和时钟，它们通常会产生新的自由度，这些自由度是由于违反了初始值约束而产生的。本文的主要目的是调查所产生的理论的性质，并了解在这种情况下，打破同胚不变性的后果。在一篇配套论文[arXiv：1504.03305]中，我们讨论了“有重以太”的一些现象学，在这种情况下，背景时钟的存在赋予以太可变的内能密度，在某些方面表现得像暗物质。
英文摘要：
We consider a class of Lorentz-violating theories of gravity involving a timelike unit vector field (the aether) coupled to a metric, two examples being Einstein-aether theory and Hořava gravity. The action always includes the Ricci scalar of the metric and the invariants quadratic in covariant derivatives of the aether, but the theories differ in how the aether is constructed from other fields, and whether those fields are varied in the action. Fields that are not varied define background structures breaking diffeomorphsim invariance, including threadings, folations, and clocks, which generally produce novel degrees of freedom arising from the violation of what would otherwise be initial value constraints. The principal aims of this paper are to survey the nature of the theories that arise, and to understand the consequences of breaking diffeomorphism invariance in this setting. In a companion paper [arXiv:1504.03305], we address some of the phenomenology of the "ponderable aether" case in which the presence of a background clock endows the aether with a variable internal energy density that behaves in some respects like dark matter.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
