论文标题
U-Dhost的内置Scordatura
Built-in scordatura in U-DHOST
论文作者
论文摘要
修改的重力理论可以容纳精确的溶液，该溶液的度量与一般相对论（即隐形溶液）具有相同的形式。这些隐形解决方案的一个问题是，当解决方案在退化的高阶标量理论中实现时，它们周围的扰动表现出很强的耦合。我们表明，在所谓的U-DHOST理论的框架的框架中，强烈的耦合问题可以绕过，在这种框架的框架中，堕落的部分被部分打破，以至于高衍生的术语仅在单位仪表中退化。从这个意义上讲，Scordatura效应通常是在U-DONSTHES中内置的。在U-DHOST理论中有一个明显的Ostrogradsky模式，但是由于它满足空距类呈超曲面上的三维椭圆微分方程，因此它不会传播。我们还阐明了这种非传播模式，即“阴影”模式在非线性级别上显示。
Modified gravity theories can accommodate exact solutions, for which the metric has the same form as the one in general relativity, i.e., stealth solutions. One problem with these stealth solutions is that perturbations around them exhibit strong coupling when the solutions are realized in degenerate higher-order scalar-tensor theories. We show that the strong coupling problem can be circumvented in the framework of the so-called U-DHOST theories, in which the degeneracy is partially broken in such a way that higher-derivative terms are degenerate only in the unitary gauge. In this sense, the scordatura effect is built-in in U-DHOST theories in general. There is an apparent Ostrogradsky mode in U-DHOST theories, but it does not propagate as it satisfies a three-dimensional elliptic differential equation on a spacelike hypersurface. We also clarify how this nonpropagating mode, i.e., the "shadowy" mode shows up at the nonlinear level.
