Inflationary predictions at small gamma
Abstract
This paper explores single field inflation models with a constant, but arbitrary speed of sound cs, obtained by deforming the kinetic energy terms to a Dirac-Born-Infeld form. Allowing cs<1 provides a simple parameterization of non-gaussianity. The dependence of inflationary observables on the parameter cs is considered in the leading order slow roll approximation. The results show that in most cases the dependence is actually rather weak for the range of cs allowed by existing bounds on non-gaussianity.
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