Warp features in DBI inflation

In Dirac-Born-Infeld inflation, changes in the sound speed that transiently break the slow-roll approximation lead to features in the power spectrum. We develop and test the generalized slow-roll approximation for calculating such effects and show that it can be extended to treat order unity features. As in slow-roll, model independent constraints on the potential of canonical inflation can be directly reinterpreted in the Dirac-Born-Infeld context through this approximation. In particular, a sharp horizon scale step in the warped brane tension can explain oscillatory features in the WMAP7 CMB power spectrum as well as features in the potential. Differences appear only as a small suppression of power on horizon scales and larger.