On the Moduli Dependence of Nonperturbative Superpotentials in Brane Inflation

TL;DR

The paper investigates how nonperturbative superpotentials in brane inflation acquire moduli dependence and how this can alleviate the inflaton mass problem. It demonstrates that one-loop 3-7 annulus corrections generate inflaton-dependent terms in the D7 gauge coupling, resolving the rho problem and yielding a φ-dependent W_nonpert that can lift flat directions. Extending to warped brane inflation, the work shows that similar corrections can flatten the potential (lower η) via a moduli-dependent quadratic φ-term, with the outcome tunable by fluxes and complex structure; a complete answer requires corrections to the Kahler potential. Overall, the results establish a concrete string-theoretic mechanism to modify the inflaton mass and potential in brane inflation models through moduli-dependent nonperturbative effects.

Abstract

We discuss string corrections to the effective potential in various models of brane inflation. These corrections contribute to the mass of the inflaton candidate and may improve its slow-roll properties. In particular, in orientifold string compactifications with dynamical D3- and D7-branes, the corrections induce inflaton dependence in the part of the superpotential that arises from gaugino condensation or other nonperturbative effects. The additional terms are in part required by supersymmetry. We explicitly discuss D3/D7-inflation, where flat directions of the potential can be lifted, and the KKLMMT model of warped brane inflation, in which the corrections open up the possibility of flattening the potential and canceling unwanted contributions to the inflaton mass.

Figures (2)

• Figure 1: The 3-7 annulus
• Figure 2: The function $\Delta$ of eq. (\ref{['r']}); for positive values the inflaton mass is lowered by the one-loop corrections to the superpotential.