Dirac Born-Infeld inflation under constant roll conditions (1807.01329v1)

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.