Journal
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
Volume -, Issue 3, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/1475-7516/2016/03/056
Keywords
inflation; non-gaussianity; physics of the early universe
Funding
- NSF [PHY-1314311, PHY-0855425]
- Institute for Advanced Study
- Direct For Mathematical & Physical Scien
- Division Of Physics [1521097] Funding Source: National Science Foundation
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Various inflationary scenarios can often be distinguished from one another by looking at the squeezed limit behavior of correlation functions. Therefore, it is useful to have a framework designed to study this limit in a more systematic and efficient way. We propose using an expansion in terms of weakly coupled super-horizon degrees of freedom, which is argued to generically exist in a near de Sitter space-time. The modes have a simple factorized form which leads to factorization of the squeezed-limit correlation functions with power law behavior in k(long)/k(short). This approach reproduces the known results in single-, quasi-single-, and multi-field inflationary models. However, it is applicable even if, unlike the above examples, the additional degrees of freedom are not weakly coupled at sub-horizon scales. Stronger results are derived in two-field (or sufficiently symmetric multi-field) inflationary models. We discuss the observability of the non-Gaussian 3-point function in the large-scale structure surveys, and argue that the squeezed limit behavior has a higher detectability chance than equilateral behavior when it scales as (k(long)/k(short))(Delta) with Delta < 1 - where local non-Gaussianity corresponds to Delta = 0.
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