Galileon Cosmology

By Nathan Chow, J. Khoury. 2009

257 citations recorded by the source corpus.

We study the cosmology of a galileon scalar-tensor theory, obtained by covariantizing the decoupling lagrangian of the Dvali-Gabadadze-Poratti (DGP) model. Despite being local in 3+1 dimensions, the resulting cosmological evolution is remarkably similar to that of the full 4+1-dimensional DGP framework, both for the expansion history and the evolution of density perturbations. As in the DGP model, the covariant galileon theory yields two branches of solutions, depending on the sign of the galileon velocity. Perturbations are stable on one branch and ghost-like on the other. An interesting effect uncovered in our analysis is a cosmological version of the Vainshtein screening mechanism: at early times, the galileon dynamics are dominated by self-interaction terms, resulting in its energy density being suppressed compared to matter or radiation; once the matter density has redshifted sufficiently, the galileon becomes an important component of the energy density and contributes to dark energy. We estimate conservatively that the resulting expansion history is consistent with the observed late-time cosmology, provided that the scale of modification satisfies rc ∼> 15 Gpc. lchow@sas.upenn.edu jkhoury@sas.upenn.edu ar X iv :0 90 5. 13 25 v4 [ he pth ] 2 2 Ju l 2 00 9

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/8c668f404824ce8dba4c08008c33c6fc17ce8e62

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Citations in the corpus

Imperfect Dark Energy from Kinetic Gravity Braiding (2010, result): “See also Refs.”
A systematic approach to generalisations of General Relativity and their cosmological implications (2018, methodology): “The covariantization of the decoupling limit of the DGP model was performed in [47].”
Dark energy or modified gravity? An effective field theory approach (2012, background): “For example, Galileon terms of the form (∇φ)2 φ [39] and more generally kinetic braiding terms of the formG(φ, (∇φ)2) φ [40] will generate it, while the full expansion of quadratic curvature invariants in this formalism will also typically generate it.”
Mimetic Gravity: A Review of Recent Developments and Applications to Cosmology and Astrophysics (2016, background): “, [272, 273]), KGB [274], Horndeski’s theory [275], and many others.”
f(R) Theories (2010, unknown): “For some models the background cosmological evolution is similar to that in the DGP model, although there are ghostlike modes depending on the sign of the time-velocity of the field π [158].”
Modified Gravity and Cosmology (2011, background): “The late time cosmology of the covariant galileon has been studied for up to cubic [299, 911], quartic [520, 23], and quintic scalar interactions [373, 956, 369].”