Generalized disformal Horndeski theories: cosmological perturbations and consistent matter coupling
Abstract
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.
Keywords
Cite
@article{arxiv.2209.02176,
title = {Generalized disformal Horndeski theories: cosmological perturbations and consistent matter coupling},
author = {Kazufumi Takahashi and Masato Minamitsuji and Hayato Motohashi},
journal= {arXiv preprint arXiv:2209.02176},
year = {2023}
}
Comments
23 pages, 2 figures