Chaotic inflation in modified gravitational theories

Antonio De Felice, Shinji Tsujikawa, Joseph Elliston, Reza Tavakol

Research output: Contribution to journalReview article

37 Citations (Scopus)

Abstract

We study chaotic inflation in the context of modified gravitational theories. Our analysis covers models based on (i) a field coupling ω(φ) with the kinetic energy X = -(1/2)gμν μφνφ and a nonmimimal coupling ζφ2R/2 with a Ricci scalar R, (ii) Brans-Dicke (BD) theories, (iii) Gauss-Bonnet (GB) gravity, and (iv) gravity with a Galileon correction. Dilatonic coupling with the kinetic energy and/or negative nonminimal coupling are shown to lead to compatibility with observations of the Cosmic Microwave Background (CMB) temperature anisotropies for the self-coupling inflaton potential V(φ) = λφ4/4. BD theory with a quadratic inflaton potential, which covers Starobinsky's f(R) model f(R) = R+R2/(6M2) with the BD parameter ωBD = 0, gives rise to a smaller tensor-to-scalar ratio for decreasing ωBD. In the presence of a GB term coupled to the field φ, we express the scalar/tensor spectral indices ns and nt as well as the tensor-to-scalar ratio r in terms of two slow-roll parameters and place bounds on the strength of the GB coupling from the joint data analysis of WMAP 7yr combined with other observations. We also study the Galileon-like self-interaction Φ(φ)Xφ with exponential coupling Φ(φ)e μφ. Using a CMB likelihood analysis we put bounds on the strength of the Galileon coupling and show that the self coupling potential can in fact be made compatible with observations in the presence of the exponential coupling with μ > 0.

Original languageEnglish
Article number021
JournalJournal of Cosmology and Astroparticle Physics
Volume2011
Issue number8
DOIs
Publication statusPublished - 2011 Aug
Externally publishedYes

Keywords

  • cosmological perturbation theory
  • inflation

ASJC Scopus subject areas

  • Astronomy and Astrophysics

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