标题： （不那么）纯粹的Lovelock Kasner度规 显示英文标题

标题： (Not so) pure Lovelock Kasner metrics

摘要： 引力相互作用预计会在极短距离下发生改变。这种情况在时空曲率普遍较大的情况下尤为重要，例如接近宇宙初始奇点时。此时，引力动力学由作用量中的高阶曲率项决定，这使得很难可靠地外推广义相对论的任何预测。本文我们将回顾Kasner型度规的纯Lovelock方程。这些方程对应于作用量中$d=2N+1,\,2N+2$维空间中的单个$N$阶Lovelock项，它们在Lovelock理论族中接近大爆炸奇点时捕捉到相关的引力动力学。这些解被分为几个各向同性类型。其中一些解族对应于退化类解，其动力学并非完全由纯Lovelock引力方程确定。相反，这些Kasner解对Lovelock级数中的次主导项变得敏感。 显示英文摘要

摘要： The gravitational interaction is expected to be modified for very short distances. This is particularly important in situations in which the curvature of spacetime is large in general, such as close to the initial cosmological singularity. The gravitational dynamics is then captured by the higher curvature terms in the action, making it difficult to reliably extrapolate any prediction of general relativity. In this note we review pure Lovelock equations for Kasner-type metrics. These equations correspond to a single $N$th order Lovelock term in the action in $d=2N+1,\,2N+2$ dimensions, and they capture the relevant gravitational dynamics when aproaching the big-bang singularity within the Lovelock family of theories. These are classified in several isotropy types. Some of these families correspond to degenerate classes of solutions, such that their dynamics is not completely determined by the equations of pure Lovelock gravity. Instead, these Kasner solutions become sensitive to the subleading terms in the Lovelock series.