论文标题
现场理论中的不稳定性：讲义注释，可转化为修改的重力
Instabilities in field theories: Lecture notes with a view into modified gravity
论文作者
论文摘要
经过修改的重力理论通常具有新的自由度，以及高阶衍生品，某些术语的错误迹象以及拉格朗日语中已经存在的复杂耦合，从一开始或源自现场重新定义需要到达爱因斯坦框架所需的现场重新定义。结果，它们非常容易提出动态不稳定性，这些动态不稳定性可能破坏在这些框架内构建可行模型的任何尝试。在这三个讲座中，我们介绍了现场理论中出现的最常见类型的不稳定性，以及一些检测它们的技术，并用几个示例补充这些内容。目的是了解具有这种病理行为的含义以及这些概念在修改重力理论中的应用。
Modified theories of gravity usually present new degrees of freedom, as well as higher order derivatives, wrong signs in certain terms and complicated couplings already present in the Lagrangian from the beginning or originated by the field redefinitions needed to reach an Einstein frame. As a consequence, they are very prone to present dynamical instabilities that could spoil any attempt to construct viable models within these frameworks. In these three lectures we introduce the most common types of instabilities that appear in field theory as well as some techniques to detect them, and supplement these contents with several examples. The goal is to understand the implications of having such pathological behaviors and the application of these notions to modified theories of gravity.
