In single-field models of inflation the effect of a long mode with momentum q reduces to a diffeomorphism at zeroth and first order in q. This gives the well-known consistency relations for the n-point functions. At order q(2) the long mode has a physical effect on the short ones, since it induces curvature, and we expect that this effect is the same as being in a curved FRW universe. In this paper we verify this intuition in various examples of the three-point function, whose behaviour at order q(2) can be written in terms of the power spectrum in a curved universe. This gives a simple alternative understanding of the level of non-Gaussianity in single-field models. Non-Gaussianity is always parametrically enhanced when modes freeze at a physical scale k(ph), (f) shorter than H: f(NL) similar to (k(ph), (f)/H)(2).
The physical squeezed limit: consistency relations at order q2 / Creminelli, Paolo; Perko, Ashley; Senatore, Leonardo; Simonovic, Marko; Trevisan, Gabriele. - In: JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS. - ISSN 1475-7516. - STAMPA. - 2013:(2013), pp. 015-015. [10.1088/1475-7516/2013/11/015]
The physical squeezed limit: consistency relations at order q2
Simonovic, Marko;
2013
Abstract
In single-field models of inflation the effect of a long mode with momentum q reduces to a diffeomorphism at zeroth and first order in q. This gives the well-known consistency relations for the n-point functions. At order q(2) the long mode has a physical effect on the short ones, since it induces curvature, and we expect that this effect is the same as being in a curved FRW universe. In this paper we verify this intuition in various examples of the three-point function, whose behaviour at order q(2) can be written in terms of the power spectrum in a curved universe. This gives a simple alternative understanding of the level of non-Gaussianity in single-field models. Non-Gaussianity is always parametrically enhanced when modes freeze at a physical scale k(ph), (f) shorter than H: f(NL) similar to (k(ph), (f)/H)(2).File | Dimensione | Formato | |
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