Testing and comparing tachyon inflation to single standard field inflation

Abstract

We compare the standard single scalar field inflationary predictions with those of an inflationary phase driven by a tachyon field. A slow-roll formalism is defined for tachyon inflation and we derive the spectra of scalar and tensor perturbations as well as the consistency relations. At lowest order the predictions of standard and tachyon inflation are the same. Higher order deviations are present and their observational relevance is discussed. We discuss the observational consequences of some typical inflationary tachyon potentials and compare them with recent data. All the models predict a negative and very small running of the scalar spectral index, and they consistently lie within the 1$\sigma$ contour of the data set. However, the regime of blue scalar spectral index and large gravity waves is not explored by these models.