Conditions for the cosmological viability of the most general scalar-tensor theories and their applications to extended Galileon dark energy models

2011

137 citations recorded by the source corpus.

In the Horndeski's most general scalar-tensor theories with second-order field equations, we derive the conditions for the avoidance of ghosts and Laplacian instabilities associated with scalar, tensor, and vector perturbations in the presence of two perfect fluids on the flat Friedmann-Lemaître-Robertson-Walker (FLRW) background. Our general results are useful for the construction of theoretically consistent models of dark energy. We apply our formulas to extended Galileon models in which a tracker solution with an equation of state smaller than -1 is present. We clarify the allowed parameter space in which the ghosts and Laplacian instabilities are absent and we numerically confirm that such models are indeed cosmologically viable.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/360f1f373ad7e591f4bd8c2a0392872ef62c709c

Citations in the corpus

• Maximal freedom at minimum cost: linear large-scale structure in general modifications of gravity (2014, unknown): “[79] where a 3+1 decomposition in the unitary gauge to obtain actions for the propagating modes: the tensors (gravitational waves) hij , the scalar ζ and the perfect-fluid matter sound waves, the last of which which we will not write out here,”
• Horndeski theory and beyond: a review (2019, unknown): “The reduced action written solely in terms of ζ and δχ takes the form [149]”
• Cosmology in generalized Proca theories (2016, unknown): “This situation is analogous to what happens in scalar Horndeski theories [94].”
• The Subaru FMOS galaxy redshift survey (FastSound). IV. New constraint on gravity theory from redshift space distortions at z ∼ 1.4 (2015, unknown): “One can generalize the covari- ant Galileon to the extended Galileon (De Felice & Tsujikawa 2012).”
• Effective field theory of dark energy: A review (2019, unknown): “Recently, it has been shown [120, 118] that among the models describing the matter action [121, 122, 114, 115, 116, 123, 117, 88, 80, 79, 82, 119], the more appropriate choice is the Sorkin-Schutz action [121, 122].”
• f(T,𝒯) gravity and cosmology (2014, unknown): “This is usual in complicated modified gravity models, for instance in generalized Galileon theory [73, 103], in Hořava-Lifshitz gravity [104, 105], in cosmology with non-minimal derivative coupling [106], etc.”