The scalar-scalar-tensor inflationary three-point function in the axion monodromy model

TL;DR

This paper derives an analytical expression for the scalar-scalar-tensor three-point function in the axion monodromy inflation model, highlighting resonance effects and consistency relations relevant for cosmological data analysis.

Contribution

It provides the first analytical template for the scalar-scalar-tensor cross-correlation in the axion monodromy model, extending previous work on scalar bi-spectrum.

Findings

Analytical expression for the scalar-scalar-tensor three-point function.

Confirmation of the consistency relation in the squeezed limit.

Enhanced non-Gaussianity due to resonance effects.

Abstract

The axion monodromy model involves a canonical scalar field that is governed by a linear potential with superimposed modulations. The modulations in the potential are responsible for a resonant behavior which gives rise to persisting oscillations in the scalar and, to a smaller extent, in the tensor power spectra. Interestingly, such spectra have been shown to lead to an improved fit to the cosmological data than the more conventional, nearly scale invariant, primordial power spectra. The scalar bi-spectrum in the model too exhibits continued modulations and the resonance is known to boost the amplitude of the scalar non-Gaussianity parameter to rather large values. An analytical expression for the scalar bi-spectrum had been arrived at earlier which, in fact, has been used to compare the model with the cosmic microwave background anisotropies at the level of three-point functions involving scalars. In this work, with future applications in mind, we arrive at a similar analytical template for the scalar-scalar-tensor cross-correlation. We also analytically establish the consistency relation (in the squeezed limit) for this three-point function. We conclude with a summary of the main results obtained.