Decoding the bispectrum of single-field inflation

Ribeiro, Raquel H and Seery, David (2011) Decoding the bispectrum of single-field inflation. Journal of Cosmology and Astroparticle Physics, 2011 (10). 027.

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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 example of DBI and k-inflation.

Item Type: Article
Additional Information: Author list in alphabetical order
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Depositing User: David Seery
Date Deposited: 06 Feb 2012 18:31
Last Modified: 29 Mar 2012 11:42
URI: http://sro.sussex.ac.uk/id/eprint/16963
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