Embedding DBI inflation in scalar-tensor theory

Understand

The Dirac-Born-Infeld (DBI) action has been widely studied as an interesting example of a model of k-inflation in which the sound speed of the cosmological perturbations differs from unity.

• In this article we consider a scalar-tensor theory in which the matter component is a field with a DBI action.
• Transforming to the Einstein frame, we explore the effect of the resulting coupling on the background dynamics of the fields and the first-order perturbations.
• We find that the coupling forces the scalar field into the minimum of its effective potential.