Combined features in the primordial spectra induced by a sudden turn in two-field DBI inflation

TL;DR

This paper explores how sharp turns in two-field DBI inflation generate unique features in the primordial spectra through mode mixing and resonance effects, with potential observational signatures.

Contribution

It provides a detailed analysis of combined features in the power spectrum and bispectrum caused by a sudden turn in two-field DBI inflation, highlighting the role of derivative interactions.

Findings

Resonance effects are less suppressed than in standard models.

Amplitude and position of features follow specific consistency relations.

Features can be tested against cosmological data.

Abstract

We investigate the features generated by a sharp turn along the inflationary trajectory in a two-field model of Dirac-Born-Infeld inflation, where one of the fields is heavy. Distinct features are generated by two different effects: the mixing of the light and heavy modes during the turn, on the one hand, and the resonance between the oscillations along the heavy direction after the turn, on the other hand. Contrary to models with standard kinetic terms, the resonance effect is not strongly suppressed because the action contains derivative interactions. Working in the potential basis, we study the oscillations after the turn and compute the amplitude of the mixing and resonance features in the power spectrum, as well as in the bispectrum for the latter effect. We find that the amplitudes and positions of these combined features obey specific consistency relations, which could be confronted with cosmological data.