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arXiv · 1111.3373

(Small) Resonant non-Gaussianities: Signatures of a Discrete Shift Symmetry in the Effective Field Theory of Inflation

Siavosh R. Behbahani·Anatoly Dymarsky·Mehrdad Mirbabayi·Leonardo Senatore
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Abstract

We apply the Effective Field Theory of Inflation to study the case where the continuous shift symmetry of the Goldstone boson πis softly broken to a discrete subgroup. This case includes and generalizes recently proposed String Theory inspired models of Inflation based on Axion Monodromy. The models we study have the property that the 2-point function oscillates as a function of the wavenumber, leading to oscillations in the CMB power spectrum. The non-linear realization of time diffeomorphisms induces some self-interactions for the Goldstone boson that lead to a peculiar non-Gaussianity whose shape oscillates as a function of the wavenumber. We find that in the regime of validity of the effective theory, the oscillatory signal contained in the n-point correlation functions, with n>2, is smaller than the one contained in the 2-point function, implying that the signature of oscillations, if ever detected, will be easier to find first in the 2-point function, and only then in the higher order correlation functions. Still the signal contained in higher-order correlation functions, that we study here in generality, could be detected at a subleading level, providing a very compelling consistency check for an approximate discrete shift symmetry being realized during inflation.

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Siavosh R. Behbahani, Anatoly Dymarsky, Mehrdad Mirbabayi, Leonardo Senatore. 2013-02-13. (Small) Resonant non-Gaussianities: Signatures of a Discrete Shift Symmetry in the Effective Field Theory of Inflation. https://doi.org/10.1088/1475-7516%2F2012%2F12%2F036

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