# Constraints on axion inflation from the weak gravity conjecture

Rudelius, Tom (Jefferson Physical Laboratory, Harvard University, Cambridge, MA 02138, U.S.A.)

30 January 2017

Abstract: We derive constraints facing models of axion inflation based on decay constant alignment from a string-theoretic and quantum gravitational perspective. In particular, we investigate the prospects for alignment and anti-alignment' of C4 axion decay constants in type IIB string theory, deriving a strict no-go result in the latter case. We discuss the relationship of axion decay constants to the weak gravity conjecture and demonstrate agreement between our string-theoretic constraints and those coming from the generalized' weak gravity conjecture. Finally, we consider a particular model of decay constant alignment in which the potential of C4 axions in type IIB compactifications on a Calabi-Yau three-fold is dominated by contributions from D7-branes, pointing out that this model evades some of the challenges derived earlier in our paper but is highly constrained by other geometric considerations.

Published in: JCAP 1509 (2015) 020