Dirac–Born–Infeld inflation under constant-roll conditions

Abstract

In this paper, we aim to generalize the constant-roll inflation in the noncanonical set-up, in the context of scalar Dirac–Born–Infeld (DBI) theory. Assuming the simplest case, when the speed of sound of scalar fluctuations is constant, we obtain exact inflationary solutions under constant-roll conditions. We finally provide an observational bound to constrain the DBI constant-roll parameter by using the values of scalar spectral index and speed of sound provided by Planck and WMAP data.