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Title: Curvature perturbation in multi-field inflation with non-minimal coupling

Abstract

In this paper we discuss a multi-field model of inflation in which generally all fields are non-minimally coupled to the Ricci scalar and have non-canonical kinetic terms. The background evolution and first-order perturbations for the model are evaluated in both the Jordan and Einstein frames, and the respective curvature perturbations compared. We confirm that they are indeed not the same - unlike in the single-field case - and also that the difference is a direct consequence of the isocurvature perturbations inherent to multi-field models. This result leads us to conclude that the notion of adiabaticity is not invariant under conformal transformations. Using a two-field example we show that even if in one frame the evolution is adiabatic, meaning that the curvature perturbation is conserved on super-horizon scales, in general in the other frame isocurvature perturbations continue to source the curvature perturbation. We also find that it is possible to realise a particular model in which curvature perturbations in both frames are conserved but with each being of different magnitude. These examples highlight that the curvature perturbation itself, despite being gauge-invariant, does not correspond directly to an observable. The non-equivalence of the two curvature perturbations would also be important when consideringmore » the addition of Standard Model matter into the system.« less

Authors:
; ;  [1]
  1. Yukawa Institute for Theoretical Physics, Kyoto University, Kitashirakawa Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan)
Publication Date:
OSTI Identifier:
22280047
Resource Type:
Journal Article
Journal Name:
Journal of Cosmology and Astroparticle Physics
Additional Journal Information:
Journal Volume: 2012; Journal Issue: 07; 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; ASTROPHYSICS; COMPARATIVE EVALUATIONS; COSMOLOGY; COUPLING; DISTURBANCES; EVOLUTION; GAUGE INVARIANCE; INFLATIONARY UNIVERSE; INFLATONS; SCALARS; STANDARD MODEL; TRANSFORMATIONS

Citation Formats

White, Jonathan, Minamitsuji, Masato, and Sasaki, Misao, E-mail: jwhite@yukawa.kyoto-u.ac.jp, E-mail: masato@yukawa.kyoto-u.ac.jp, E-mail: misao@yukawa.kyoto-u.ac.jp. Curvature perturbation in multi-field inflation with non-minimal coupling. United States: N. p., 2012. Web. doi:10.1088/1475-7516/2012/07/039.
White, Jonathan, Minamitsuji, Masato, & Sasaki, Misao, E-mail: jwhite@yukawa.kyoto-u.ac.jp, E-mail: masato@yukawa.kyoto-u.ac.jp, E-mail: misao@yukawa.kyoto-u.ac.jp. Curvature perturbation in multi-field inflation with non-minimal coupling. United States. doi:10.1088/1475-7516/2012/07/039.
White, Jonathan, Minamitsuji, Masato, and Sasaki, Misao, E-mail: jwhite@yukawa.kyoto-u.ac.jp, E-mail: masato@yukawa.kyoto-u.ac.jp, E-mail: misao@yukawa.kyoto-u.ac.jp. Sun . "Curvature perturbation in multi-field inflation with non-minimal coupling". United States. doi:10.1088/1475-7516/2012/07/039.
@article{osti_22280047,
title = {Curvature perturbation in multi-field inflation with non-minimal coupling},
author = {White, Jonathan and Minamitsuji, Masato and Sasaki, Misao, E-mail: jwhite@yukawa.kyoto-u.ac.jp, E-mail: masato@yukawa.kyoto-u.ac.jp, E-mail: misao@yukawa.kyoto-u.ac.jp},
abstractNote = {In this paper we discuss a multi-field model of inflation in which generally all fields are non-minimally coupled to the Ricci scalar and have non-canonical kinetic terms. The background evolution and first-order perturbations for the model are evaluated in both the Jordan and Einstein frames, and the respective curvature perturbations compared. We confirm that they are indeed not the same - unlike in the single-field case - and also that the difference is a direct consequence of the isocurvature perturbations inherent to multi-field models. This result leads us to conclude that the notion of adiabaticity is not invariant under conformal transformations. Using a two-field example we show that even if in one frame the evolution is adiabatic, meaning that the curvature perturbation is conserved on super-horizon scales, in general in the other frame isocurvature perturbations continue to source the curvature perturbation. We also find that it is possible to realise a particular model in which curvature perturbations in both frames are conserved but with each being of different magnitude. These examples highlight that the curvature perturbation itself, despite being gauge-invariant, does not correspond directly to an observable. The non-equivalence of the two curvature perturbations would also be important when considering the addition of Standard Model matter into the system.},
doi = {10.1088/1475-7516/2012/07/039},
journal = {Journal of Cosmology and Astroparticle Physics},
issn = {1475-7516},
number = 07,
volume = 2012,
place = {United States},
year = {2012},
month = {7}
}