Dirac Born-Infeld inflation under constant roll conditions

TL;DR

This paper extends constant-roll inflation models to the Dirac-Born-Infeld framework, deriving exact solutions with constant but non-unity sound speed, and compares predictions with observational data.

Contribution

It introduces exact solutions for constant-roll inflation in the DBI setup with constant sound speed, expanding the theoretical understanding of string-inspired inflation models.

Findings

Inflationary solutions are attractors under constant-roll conditions.

Power spectra analysis aligns with observational bounds from Planck and WMAP.

Derived constraints on the DBI constant roll parameter based on observational data.

Abstract

In the present paper, we aim to generalize the constant-roll inflation in the non-canonical set-up, particularly in the context of scalar Dirac-Born-Infeld (DBI) theory which has emerged to be prospective candidate for describing inflation in the realm of string theory and in general permits time dependent speed of sound. Assuming the simplest case, when the speed of sound of scalar fluctuations is constant but different from unity, we obtain exact inflationary solutions and corresponding solutions of warp factors under constant-roll conditions. In this scenario, the inflationary solution is found to be an attractor. The power spectra of curvature fluctuations is analysed in the DBI regime and finally an estimation for predicting the observational bound on the DBI constant roll parameter is performed by using the the values of scalar spectral index and speed of sound provided by Planck and WMAP data.