Dirac-Born-Infeld and k-inflation: the CMB anisotropies from string theory

Understand

Inflationary models within string theory exhibit unusual scalar field dynamics involving non-minimal kinetic terms and generically referred to as k-inflation.

• In this situation, the standard slow-roll approach used to determine the behavior of the primordial cosmological perturbations cannot longer be used.
• We present a generic method, based on the uniform approximation, to analytically derive the primordial power spectra of scalar and tensor perturbations.
• At leading order, the scalar spectral index, its running and the tensor-to-scalar ratio are modified by the new dynamics.