Spinflation with backreaction

We study brane inflation in flux compactifications at the nonlinear level, solving the D3-brane DBI-equations of motion including backreaction from the D3-D7 brane potential and from perturbations of the warp factor. We first numerically compute the exact functional form of the Kaehler modulus valid on the entire supergravity background and obtain a two-field potential along radial and harmonic directions. We find that a valid perturbative expansion on the entire supergravity background with the Kaehler modulus integrated out adiabatically in DBI inflation requires hierarchies of scales that determine compactification parameters different from those typical in slow-roll models. Our numerical results then show that the DBI inflationary solutions are quite robust against these nonlinear corrections.