Exploring gravitational theories beyond Horndeski
Abstract
We have recently proposed a new class of gravitational scalar-tensor theories free from Ostrogradski instabilities, in arXiv:1404.6495. As they generalize Horndeski theories, or "generalized" galileons, we call them G. These theories possess a simple formulation when the time hypersurfaces are chosen to coincide with the uniform scalar field hypersurfaces. We confirm that they contain only three propagating degrees of freedom by presenting the details of the Hamiltonian formulation. We examine the coupling between these theories and matter. Moreover, we investigate how they transform under a disformal redefinition of the metric. Remarkably, these theories are preserved by disformal transformations that depend on the scalar field gradient, which also allow to map subfamilies of G into Horndeski theories.
Keywords
Cite
@article{arxiv.1408.1952,
title = {Exploring gravitational theories beyond Horndeski},
author = {Jérôme Gleyzes and David Langlois and Federico Piazza and Filippo Vernizzi},
journal= {arXiv preprint arXiv:1408.1952},
year = {2015}
}
Comments
33 pages, added comments and corrected typos as in JCAP version