DBI-Curvaton

TL;DR

This work analyzes a curvaton model governed by a Dirac-Born-Infeld-like action, deriving how non-canonical kinetics modify the perturbation spectrum and non-Gaussianity. It shows that isocurvature modes are suppressed by the sound speed $c_s$, but after conversion the curvature perturbation is enhanced roughly as $c_s^{-3/2}$, and the local non-Gaussianity $f_{NL}$ attains values around $O(10)$. The curvature perturbation generation proceeds through a tachyon-condensate exit, tying the result to the warp factor $f(sigma)$ rather than the potential. These findings imply potentially lower inflation scales in DBI-curvaton scenarios and highlight a bridge between brane cosmology and observable curvature perturbations via non-Gaussianity.

Abstract

In this paper, we study a curvaton model described by a Dirac-Born-Infeld-like action. We calculate the spectrum of curvature perturbation induced by DBI-curvaton and estimate its non-Gaussianity. We find that in the limit of low sound speed the amplitude of curvature perturbation is enhanced more than that in DBI inflation. This result also means that the inflationary scale with DBI-curvaton may be lower than that in usual curvaton model. In addition, we also find that the local non-Gaussianity level in DBI-curvaton is generally about 10 times larger than that in usual curvaton model, which is interesting for current observations. This work in some sense explores a new application of brane-cosmology in inflation.