Evolution of linear cosmological perturbations and its observational implications in Galileon-type modified gravity

Journal Article · Mon Mar 15 00:00:00 EDT 2010 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.81.063513· OSTI ID:21409380

Kobayashi, Tsutomu; Suzuki, Daichi ^[1]; Tashiro, Hiroyuki ^[2]

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1. Department of Physics, Waseda University, Okubo 3-4-1, Shinjuku, Tokyo 169-8555 (Japan)
2. Center for Particle Physics and Phenomenology (CP3), Universite Catholique de Louvain, Chemin du Cyclotron, 2, B-1348 Louvain-la-Neuve (Belgium)

A scalar-tensor theory of gravity can be made not only to account for the current cosmic acceleration, but also to satisfy solar-system and laboratory constraints, by introducing a nonlinear derivative interaction for the scalar field. Such an additional scalar degree of freedom is called 'Galileon'. The basic idea is inspired by the Dvali-Gabadadze-Porrati braneworld, but one can construct a ghost-free model that admits a self-accelerating solution. We perform a fully relativistic analysis of linear perturbations in Galileon cosmology. Although the Galileon model can mimic the background evolution of standard {Lambda}CDM cosmology, the behavior of perturbation is quite different. It is shown that there exists a superhorizon growing mode in the metric and Galileon perturbations at early times, suggesting that the background is unstable. A fine-tuning of the initial condition for the Galileon fluctuation is thus required in order to promote a desirable evolution of perturbations at early times. Assuming the safe initial condition, we then compute the late-time evolution of perturbations and discuss observational implications in Galileon cosmology. In particular, we find anticorrelations in the cross correlation of the integrated Sachs-Wolfe effect and large scale structure, similar to the normal branch of the Dvali-Gabadadze-Porrati model.

• OSTI ID: 21409380
• Journal Information: Physical Review. D, Particles Fields, Vol. 81, Issue 6; Other Information: DOI: 10.1103/PhysRevD.81.063513; (c) 2010 The American Physical Society; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCELERATION
BRANES
CORRELATIONS
COSMOLOGY
DEGREES OF FREEDOM
DISTURBANCES
FLUCTUATIONS
GRAVITATION
INTERACTIONS
MATHEMATICAL SOLUTIONS
METRICS
M-THEORY
NONLINEAR PROBLEMS
PERTURBATION THEORY
RELATIVISTIC RANGE
SCALAR FIELDS
SOLAR SYSTEM
ENERGY RANGE
VARIATIONS