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

Kobayashi, Tsutomu; Suzuki, Daichi; Tashiro, Hiroyuki

doi:10.1103/PHYSREVD.81.063513

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

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Abstract

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.

Authors:

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

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

Publication Date:: Mon Mar 15 00:00:00 EDT 2010

OSTI Identifier:: 21409380

Resource Type:: Journal Article

Journal Name:: Physical Review. D, Particles Fields

Additional Journal Information:: Journal Volume: 81; Journal Issue: 6; Other Information: DOI: 10.1103/PhysRevD.81.063513; (c) 2010 The American Physical Society; Journal ID: ISSN 0556-2821

Country of Publication:: United States

Language:: English

Subject:: 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

Citation Formats


                    Kobayashi, Tsutomu, Suzuki, Daichi, and Tashiro, Hiroyuki. Evolution of linear cosmological perturbations and its observational implications in Galileon-type modified gravity.  United States: N. p., 2010. 
        Web.  doi:10.1103/PHYSREVD.81.063513.

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                    Kobayashi, Tsutomu, Suzuki, Daichi, & Tashiro, Hiroyuki. Evolution of linear cosmological perturbations and its observational implications in Galileon-type modified gravity.  United States.  https://doi.org/10.1103/PHYSREVD.81.063513

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                    Kobayashi, Tsutomu, Suzuki, Daichi, and Tashiro, Hiroyuki. 2010.  
        "Evolution of linear cosmological perturbations and its observational implications in Galileon-type modified gravity".  United States.  https://doi.org/10.1103/PHYSREVD.81.063513.

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@article{osti_21409380,

  title        = {Evolution of linear cosmological perturbations and its observational implications in Galileon-type modified gravity},

  author       = {Kobayashi, Tsutomu and Suzuki, Daichi and Tashiro, Hiroyuki},

  abstractNote = {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.},

  doi          = {10.1103/PHYSREVD.81.063513},

  url          = {https://www.osti.gov/biblio/21409380},
  journal      = {Physical Review. D, Particles Fields},

  issn         = {0556-2821},

  number       = 6,

  volume       = 81,

  place        = {United States},

  year         = {Mon Mar 15 00:00:00 EDT 2010},

  month        = {Mon Mar 15 00:00:00 EDT 2010}

}

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