One-loop Pfaffians and large-field inflation in string theory

Abstract: We study the consistency of large-field inflation in low-energy effective field theories of string theory. In particular, we focus on the stability of K\"ahler moduli in the particularly interesting case where the non-perturbative superpotential of the K\"ahler sector explicitly depends on the inflaton field. This situation arises generically due to one-loop corrections to the instanton action. The field dependence of the modulus potential feeds back into the inflationary dynamics, potentially impairing slow roll. We distinguish between world-sheet instantons from Euclidean D-branes, which typically yield polynomial one-loop Pfaffians, and gaugino condensates, which can yield exponential or periodic corrections. In all scenarios successful slow-roll inflation imposes bounds on the magnitude of the one-loop correction, corresponding to constraints on possible compactifications. While we put a certain emphasis on Type IIB constructions with mobile D7-branes, our results seem to apply more generally.