Inflationary predictions at small gamma

Understand

This paper explores single field inflation models with a constant, but arbitrary speed of sound c_s, obtained by deforming the kinetic energy terms to a Dirac-Born-Infeld form.

• Allowing c_s<1 provides a simple parameterization of non-gaussianity.
• The dependence of inflationary observables on the parameter c_s 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 c_s allowed by existing bounds on non-gaussianity.