Generalized disformal Horndeski theories: Cosmological perturbations and consistent matter coupling
Generalized disformal Horndeski theories: Cosmological perturbations and consistent matter coupling
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DOI：
10.1093/ptep/ptac161
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发表时间：
2022-09
影响因子：
3.5
通讯作者：
Kazufumi Takahashi;Masato Minamitsuji;H. Motohashi
中科院分区：
文献类型：
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作者：
Kazufumi Takahashi;Masato Minamitsuji;H. Motohashi
可逆非形式变换是研究无鬼标量张量理论的有用工具。通过对 Horndeski 理论进行可逆不形式变换的高导数推广，我们构建了一类新的无幽灵标量张量理论，我们将其称为广义不形式 Horndeski 理论。具体来说，这些理论超出了二次/三次 DHOST 类。我们探索宇宙学扰动，以确定引力波以光速传播的子类，并阐明张量和标量扰动不存在鬼影/梯度不稳定性的条件。我们还研究了物质场可以与这些理论一致耦合而不引入不需要的额外自由度的条件。
Invertible disformal transformations are a useful tool to investigate ghost-free scalar–tensor theories. By performing a higher-derivative generalization of the invertible disformal transformation on Horndeski theories, we construct a novel class of ghost-free scalar–tensor theories, which we dub generalized disformal Horndeski theories. Specifically, these theories lie beyond the quadratic/cubic DHOST class. We explore cosmological perturbations to identify a subclass where gravitational waves propagate at the speed of light and clarify the conditions for the absence of ghost/gradient instabilities for tensor and scalar perturbations. We also investigate the conditions under which a matter field can be consistently coupled to these theories without introducing unwanted extra degrees of freedom.