Evolution of fNL to the adiabatic limit

Elliston, Joseph, Mulryne, David J, Seery, David and Tavakol, Reza (2011) Evolution of fNL to the adiabatic limit. Journal of Cosmology and Astroparticle Physics, 2011 (11). 005. ISSN 1990-3413

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We study inflationary perturbations in multiple-field models, for which zeta typically evolves until all isocurvature modes decay--the "adiabatic limit'". We use numerical methods to explore the sensitivity of the nonlinear parameter fNL to the process by which this limit is achieved, finding an appreciable dependence on model-specific data such as the time at which slow-roll breaks down or the timescale of reheating. In models with a sum-separable potential where the isocurvature modes decay before the end of the slow-roll phase we give an analytic criterion for the asymptotic value of fNL to be large. Other examples can be constructed using a waterfall field to terminate inflation while fNL is transiently large, caused by descent from a ridge or convergence into a valley. We show that these two types of evolution are distinguished by the sign of the bispectrum, and give approximate expressions for the peak fNL.

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 21:13
Last Modified: 03 Apr 2012 13:50
URI: http://srodev.sussex.ac.uk/id/eprint/30320
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