# Exploring gravitational theories beyond Horndeski

Abstract : We have recently proposed a new class of gravitational scalar-tensor theories free from ghost instabilities. As they generalize Horndeski theories, or "generalized" galileons, we call them G$^3$. These theories possess a simple formulation when the time hypersurfaces are chosen to coincide with the uniform scalar field hypersurfaces. We confirm that they do not suffer from Ostrogradski instabilities 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, which also allow subfamilies of G$^3$ to be mapped into Horndeski theories.
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https://hal-cea.archives-ouvertes.fr/cea-01073383
Contributor : Emmanuelle de Laborderie Connect in order to contact the contributor
Submitted on : Thursday, October 9, 2014 - 4:04:14 PM
Last modification on : Monday, December 13, 2021 - 9:16:03 AM

### Identifiers

• HAL Id : cea-01073383, version 1
• ARXIV : 1408.1952

### Citation

Jérôme Gleyzes, David Langlois, Federico Piazza, Filippo Vernizzi. Exploring gravitational theories beyond Horndeski. 2014. ⟨cea-01073383⟩

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