skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Primordial non-gaussianities in general modified gravitational models of inflation

Abstract

We compute the three-point correlation function of primordial scalar density perturbations in a general single-field inflationary scenario, where a scalar field φ has a direct coupling with the Ricci scalar R and the Gauss-Bonnet term G. Our analysis also covers the models in which the Lagrangian includes a function non-linear in the field kinetic energy X = −(∂φ){sup 2}/2, and a Galileon-type field self-interaction G(φ,X)□φ, where G is a function of φ and X. We provide a general analytic formula for the equilateral non-Gaussianity parameter f{sub NL}{sup equil} associated with the bispectrum of curvature perturbations. A quasi de Sitter approximation in terms of slow-variation parameters allows us to derive a simplified form of f{sub NL}{sup equil} convenient to constrain various inflation models observationally. If the propagation speed of the scalar perturbations is much smaller than the speed of light, the Gauss-Bonnet term as well as the Galileon-type field self-interaction can give rise to large non-Gaussianities testable in future observations. We also show that, in Brans-Dicke theory with a field potential (including f(R) gravity), f{sub NL}{sup equil} is of the order of slow-roll parameters as in standard inflation driven by a minimally coupled scalar field.

Authors:
;  [1]
  1. Department of Physics, Faculty of Science, Tokyo University of Science, 1-3, Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan)
Publication Date:
OSTI Identifier:
22277683
Resource Type:
Journal Article
Journal Name:
Journal of Cosmology and Astroparticle Physics
Additional Journal Information:
Journal Volume: 2011; Journal Issue: 04; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1475-7516
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; APPROXIMATIONS; BRANES; CORRELATION FUNCTIONS; COSMOLOGY; COUPLING; DE SITTER GROUP; DE SITTER SPACE; DENSITY; DISTURBANCES; GRAVITATION; INFLATIONARY UNIVERSE; KINETIC ENERGY; LAGRANGIAN FUNCTION; NONLINEAR PROBLEMS; POTENTIALS; SCALAR FIELDS; VISIBLE RADIATION

Citation Formats

Felice, Antonio De, and Tsujikawa, Shinji. Primordial non-gaussianities in general modified gravitational models of inflation. United States: N. p., 2011. Web. doi:10.1088/1475-7516/2011/04/029.
Felice, Antonio De, & Tsujikawa, Shinji. Primordial non-gaussianities in general modified gravitational models of inflation. United States. https://doi.org/10.1088/1475-7516/2011/04/029
Felice, Antonio De, and Tsujikawa, Shinji. 2011. "Primordial non-gaussianities in general modified gravitational models of inflation". United States. https://doi.org/10.1088/1475-7516/2011/04/029.
@article{osti_22277683,
title = {Primordial non-gaussianities in general modified gravitational models of inflation},
author = {Felice, Antonio De and Tsujikawa, Shinji},
abstractNote = {We compute the three-point correlation function of primordial scalar density perturbations in a general single-field inflationary scenario, where a scalar field φ has a direct coupling with the Ricci scalar R and the Gauss-Bonnet term G. Our analysis also covers the models in which the Lagrangian includes a function non-linear in the field kinetic energy X = −(∂φ){sup 2}/2, and a Galileon-type field self-interaction G(φ,X)□φ, where G is a function of φ and X. We provide a general analytic formula for the equilateral non-Gaussianity parameter f{sub NL}{sup equil} associated with the bispectrum of curvature perturbations. A quasi de Sitter approximation in terms of slow-variation parameters allows us to derive a simplified form of f{sub NL}{sup equil} convenient to constrain various inflation models observationally. If the propagation speed of the scalar perturbations is much smaller than the speed of light, the Gauss-Bonnet term as well as the Galileon-type field self-interaction can give rise to large non-Gaussianities testable in future observations. We also show that, in Brans-Dicke theory with a field potential (including f(R) gravity), f{sub NL}{sup equil} is of the order of slow-roll parameters as in standard inflation driven by a minimally coupled scalar field.},
doi = {10.1088/1475-7516/2011/04/029},
url = {https://www.osti.gov/biblio/22277683}, journal = {Journal of Cosmology and Astroparticle Physics},
issn = {1475-7516},
number = 04,
volume = 2011,
place = {United States},
year = {2011},
month = {4}
}