Exploring gravitational theories beyond Horndeski

Jérôme Gleyzes (1) , David Langlois (2) , Federico Piazza (3, 4) , Filippo Vernizzi (1)

1 CEA - Commissariat à l'énergie atomique et aux énergies alternatives
2 APC (UMR_7164) - AstroParticule et Cosmologie
3 CPT - Centre de Physique Théorique - UMR 7332
4 CPT - E3 Cosmologie

We have recently proposed a new class of gravitational scalar-tensor theories free from Ostro-gradski instabilities, in Ref. [1]. 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 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 3 into Horndeski theories.

Domaines: Relativité Générale et Cosmologie Quantique [gr-qc]; Physique des Hautes Energies - Théorie [hep-th]

Jérôme Gleyzes, David Langlois, Federico Piazza, Filippo Vernizzi. Exploring gravitational theories beyond Horndeski. Journal of Cosmology and Astroparticle Physics, 2015, 2015 (02), pp.018. ⟨10.1088/1475-7516/2015/02/018⟩. ⟨hal-01261098⟩