DBI inflation and warped black holes

We study a possible amplification mechanism for the curvature perturbations generated during inflation by a Dirac-Born-Infeld (DBI) inflaton in the presence of a sharp feature in the warp factor. The large growth resulting in the scalar power spectrum is a consequence of the decreasing speed of sound. We obtain analytical approximate expressions for the relevant dynamical quantities both in the slow roll phase and during the transient phase which leads to the amplification. We finally compare our approximations to the exact numerical evolution and give, in such a context, the general rules for building a viable inflationary model leading to, during the subsequent radiation dominated era, an abundant primordial black holes formation.

Automated summary

This study examines a possible amplification mechanism for curvature perturbations generated during inflation by a Dirac-Born-Infeld (DBI) inflaton in the presence of a sharp feature in the warp factor. The large growth in the scalar power spectrum is a result of the decreasing speed of sound. Analytical approximate expressions for relevant dynamical quantities in both the slow roll phase and the transient phase leading to amplification are obtained. Finally, a comparison is made between the approximations and the exact numerical evolution, and general rules for building a viable inflationary model that leads to abundant primordial black hole formation during the subsequent radiation dominated era are given.