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Title: Decoding the bispectrum of single-field inflation

Abstract

Galileon fields arise naturally from the decoupling limit of massive gravities, and possess special self-interactions which are protected by a spacetime generalization of Galilean symmetry. We briefly revisit the inflationary phenomenology of Galileon theories. Working from recent computations of the fluctuation Lagrangian to cubic order in the most general model with second-order equations of motion, we show that a distinct shape is present but with suppressed amplitude. A similar shape has been found in other higher-derivative models. It may be visible in a theory tuned to suppress the leading-order shapes, or if the overall bispectrum has large amplitude. Using a partial-wave expansion of the bispectrum, we suggest a possible origin for the frequent appearance of this shape. It follows that models with very disparate microphysics can produce very similar bispectra. We argue that it may be more profitable to distinguish these models by searching for relations between the amplitudes of these common shapes. We illustrate this method using the examples of DBI and k-inflation.

Authors:
 [1];  [2]
  1. Department of Applied Mathematics and Theoretical Physics Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)
  2. Astronomy Centre, University of Sussex, Falmer, Brighton BN1 9QH (United Kingdom)
Publication Date:
OSTI Identifier:
22280237
Resource Type:
Journal Article
Journal Name:
Journal of Cosmology and Astroparticle Physics
Additional Journal Information:
Journal Volume: 2011; Journal Issue: 10; 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; BORN-INFELD THEORY; CALCULATION METHODS; COSMOLOGY; DECOUPLING; EQUATIONS OF MOTION; FLUCTUATIONS; GRAVITATION; INFLATIONARY UNIVERSE; LAGRANGIAN FUNCTION; PARTIAL WAVES; SPACE-TIME; SYMMETRY

Citation Formats

Ribeiro, Raquel H., and Seery, David, E-mail: R.Ribeiro@damtp.cam.ac.uk, E-mail: D.Seery@sussex.ac.uk. Decoding the bispectrum of single-field inflation. United States: N. p., 2011. Web. doi:10.1088/1475-7516/2011/10/027.
Ribeiro, Raquel H., & Seery, David, E-mail: R.Ribeiro@damtp.cam.ac.uk, E-mail: D.Seery@sussex.ac.uk. Decoding the bispectrum of single-field inflation. United States. doi:10.1088/1475-7516/2011/10/027.
Ribeiro, Raquel H., and Seery, David, E-mail: R.Ribeiro@damtp.cam.ac.uk, E-mail: D.Seery@sussex.ac.uk. Sat . "Decoding the bispectrum of single-field inflation". United States. doi:10.1088/1475-7516/2011/10/027.
@article{osti_22280237,
title = {Decoding the bispectrum of single-field inflation},
author = {Ribeiro, Raquel H. and Seery, David, E-mail: R.Ribeiro@damtp.cam.ac.uk, E-mail: D.Seery@sussex.ac.uk},
abstractNote = {Galileon fields arise naturally from the decoupling limit of massive gravities, and possess special self-interactions which are protected by a spacetime generalization of Galilean symmetry. We briefly revisit the inflationary phenomenology of Galileon theories. Working from recent computations of the fluctuation Lagrangian to cubic order in the most general model with second-order equations of motion, we show that a distinct shape is present but with suppressed amplitude. A similar shape has been found in other higher-derivative models. It may be visible in a theory tuned to suppress the leading-order shapes, or if the overall bispectrum has large amplitude. Using a partial-wave expansion of the bispectrum, we suggest a possible origin for the frequent appearance of this shape. It follows that models with very disparate microphysics can produce very similar bispectra. We argue that it may be more profitable to distinguish these models by searching for relations between the amplitudes of these common shapes. We illustrate this method using the examples of DBI and k-inflation.},
doi = {10.1088/1475-7516/2011/10/027},
journal = {Journal of Cosmology and Astroparticle Physics},
issn = {1475-7516},
number = 10,
volume = 2011,
place = {United States},
year = {2011},
month = {10}
}