TY - JOUR
T1 - Matter perturbations in Galileon cosmology
AU - De Felice, Antonio
AU - Kase, Ryotaro
AU - Tsujikawa, Shinji
PY - 2011/2/17
Y1 - 2011/2/17
N2 - We study the evolution of matter density perturbations in Galileon cosmology where the late-time cosmic acceleration can be realized by a field kinetic energy. We obtain full perturbation equations at linear order in the presence of five covariant Lagrangians Li (i=1,5) satisfying the Galileon symmetry ∂μφ→∂μφ +bμ in the flat space-time. The equations for a matter perturbation as well as an effective gravitational potential are derived under a quasistatic approximation on subhorizon scales. This approximation can reproduce full numerical solutions with high accuracy for the wavelengths relevant to large-scale structures. For the model parameters constrained by the background expansion history of the Universe, the growth rate of matter perturbations is larger than that in the Λ-cold dark matter model, with the growth index γ today typically smaller than 0.4. We also find that, even on very large scales associated with the integrated-Sachs-Wolfe effect in cosmic microwave background temperature anisotropies, the effective gravitational potential exhibits a temporal growth during the transition from the matter era to the epoch of cosmic acceleration. These properties are useful to distinguish the Galileon model from the Λ-cold dark matter model in future high-precision observations.
AB - We study the evolution of matter density perturbations in Galileon cosmology where the late-time cosmic acceleration can be realized by a field kinetic energy. We obtain full perturbation equations at linear order in the presence of five covariant Lagrangians Li (i=1,5) satisfying the Galileon symmetry ∂μφ→∂μφ +bμ in the flat space-time. The equations for a matter perturbation as well as an effective gravitational potential are derived under a quasistatic approximation on subhorizon scales. This approximation can reproduce full numerical solutions with high accuracy for the wavelengths relevant to large-scale structures. For the model parameters constrained by the background expansion history of the Universe, the growth rate of matter perturbations is larger than that in the Λ-cold dark matter model, with the growth index γ today typically smaller than 0.4. We also find that, even on very large scales associated with the integrated-Sachs-Wolfe effect in cosmic microwave background temperature anisotropies, the effective gravitational potential exhibits a temporal growth during the transition from the matter era to the epoch of cosmic acceleration. These properties are useful to distinguish the Galileon model from the Λ-cold dark matter model in future high-precision observations.
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U2 - 10.1103/PhysRevD.83.043515
DO - 10.1103/PhysRevD.83.043515
M3 - Article
AN - SCOPUS:79952214993
VL - 83
JO - Physical Review D - Particles, Fields, Gravitation and Cosmology
JF - Physical Review D - Particles, Fields, Gravitation and Cosmology
SN - 1550-7998
IS - 4
M1 - 043515
ER -