Enhanced Inflation in the Dirac-Born-Infeld framework

TL;DR

This paper explores inflationary scenarios within the Dirac-Born-Infeld framework by applying symmetry transformations to derive solutions, analyze perturbations, and identify broad classes of inflationary behaviors.

Contribution

It introduces a novel application of form invariance symmetry transformations to the DBI inflationary model, deriving new solutions and analyzing perturbation spectra.

Findings

Derived inflationary solutions with exponential potentials

Analyzed scalar and tensor perturbation spectra transformations

Identified broad classes of power-law inflationary solutions

Abstract

We consider the Einstein equations within the DBI scenario for a spatially flat Friedmann-Robertson-Walker (FRW) spacetime without a cosmological constant. We derive the inflationary scenario by applying the symmetry transformations which preserve the form of the Friedmann and conservation equations. These form invariance transformations generate a symmetry group parametrized by the Lorentz factor $\ga$. We explicitly obtain an inflationary scenario by the cooperative effect of adding energy density into the Friedmann equation. For the case of a constant Lorentz factor, and under the slow roll assumption, we find the transformation rules for the scalar and tensor power spectra of perturbations as well as their ratio under the action of the form invariance symmetry group. Within this case and due to its relevance for the inflationary paradigm, we find the general solution of the dynamical equations for a DBI field driven by an exponential potential and show a broad set of inflationary solutions. The general solution can be split into three subsets and all these behave asymptotically as a power law solution at early and at late times.