Inflation in DBI models with constant gamma

Abstract

Dirac-Born-Infeld scalar field theories which appear in the context of inflation in string theory in general have a field dependent speed of sound. It is however possible to write down DBI models which possess exact solutions characterized by a constant speed of sound different from unity. This requires that the potential and the effective D-brane tension appearing in a DBI action have to be related in a specific way. This paper describes such models in general and presents some examples with a constant speed of sound $c_s<1$ for which the spectrum of scalar perturbations can be found analytically without resorting to the slow roll approximation.

V3: Extended and improved discussion, some new results, and additional references. V4: small improvements; same as the version published in JCAP

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Cited by in corpus (2)

• K-inflationary Power Spectra in the Uniform Approximation
• Inflationary potentials in DBI models