K-inflationary Power Spectra in the Uniform Approximation

Understand

The advent of explicit Dirac-Born-Infeld (DBI) inflationary models within string theory has drawn renewed interest to the cosmological role of unusual scalar field dynamics, usually referred to as k-inflation.

• In this situation, the standard method used to determine the behavior of cosmological perturbations breaks down.
• We present a generic method, based on the uniform approximation, to analytically derive the power spectra of scalar and tensor perturbations.
• For this purpose, a simple hierarchy of parameters, related to the sound speed of the cosmological fluctuations and its successive derivatives, is introduced in a k-inflation analogue of the Hubble flow functions.