标题： Lovelock引力中的宇宙模型：近期进展概述 显示英文标题

标题： Cosmological Models in Lovelock Gravity: An Overview of Recent Progress

摘要： 在当前的综述中，我们总结了额外维度 Lovelock 引力宇宙学方面的最新进展。 我们的综述涵盖了各种特定模型/物质源组合： 包括爱因斯坦–高斯–博内引力以及带有真空、宇宙常数、完美流体、空间曲率及其某些组合的三次 Lovelock 引力。 我们的分析表明，可以通过简单地要求从初始奇点到现实低能态的平滑过渡来对上述模型的参数设置约束。 最初，各向异性空间自然演化为两个各向同性子空间的配置，如果其中一个子空间是三维且正在膨胀，而另一个正在收缩，我们称之为现实紧致化。 当然，这一过程并非毫无障碍，在本文中，我们回顾了针对上述模型紧致化的研究结果。 特别是，对于真空和$\Lambda$-项 EGB 模型，如果额外维度的数量是$D \geqslant 2$，则紧致化不会被抑制（但也不是唯一可能的结果）；对于真空三次 Lovelock 引力，它总是存在（然而，三次 Lovelock 引力仅在$D \geqslant 3$个额外维度下定义）；对于具有完美流体的 EGB 模型，在$D=2$时它存在（我们尚未考虑更高维度下的该模型）；而在存在空间曲率的情况下，额外维度的实际稳定始终存在（然而，这种模型仅在$D \geqslant 4$个额外维度下是良好的）。 显示英文摘要

摘要： In the current review, we provide a summary of the recent progress made in the cosmological aspect of extra-dimensional Lovelock gravity. Our review covers a wide variety of particular model/matter source combinations: Einstein--Gauss--Bonnet as well as cubic Lovelock gravities with vacuum, cosmological constant, perfect fluid, spatial curvature, and some of their combinations. Our analysis suggests that it is possible to set constraints on the parameters of the above-mentioned models from the simple requirement of the existence of a smooth transition from the initial singularity to a realistic low-energy regime. Initially, anisotropic space naturally evolves into a configuration with two isotropic subspaces, and if one of these subspaces is three-dimensional and is expanding while another is contracting, we call it realistic compactification. Of course, the process is not devoid of obstacles, and in our paper, we review the results of the compactification occurrence investigation for the above-mentioned models. In particular, for vacuum and $\Lambda$-term EGB models, compactification is not suppressed (but is not the only possible outcome either) if the number of extra dimensions is $D \geqslant 2$; for vacuum cubic Lovelock gravities it is always present (however, cubic Lovelock gravity is defined only for $D \geqslant 3$ number of extra dimensions); for the EGB model with perfect fluid it is present for $D=2$ (we have not considered this model in higher dimensions yet), and in the presence of spatial curvature, the realistic stabilization of extra dimensions is always present (however, such a model is well-defined only in $D \geqslant 4$ number of extra dimensions).