Galileon cosmology
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States) and Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada)
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 ghostlike 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 r{sub c} > or approx. 15 Gpc.
- OSTI ID:
- 21316260
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 80, Issue 2; Other Information: DOI: 10.1103/PhysRevD.80.024037; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COMPUTERIZED SIMULATION
COSMOLOGY
DECOUPLING
DENSITY
DISTURBANCES
ENERGY DENSITY
EVOLUTION
INTERACTIONS
LAGRANGIAN FUNCTION
MATHEMATICAL SOLUTIONS
NONLUMINOUS MATTER
ONE-DIMENSIONAL CALCULATIONS
PERTURBATION THEORY
VELOCITY