Large Field Inflation from Axion Mixing

TL;DR

This paper explores how multi-axion systems in string theory can achieve large field inflation through axion mixing mechanisms, avoiding the need for alignment of decay constants.

Contribution

It introduces a novel mechanism for large field inflation via axion mixing in string theory, bypassing the alignment requirement and analyzing associated gauge consistency conditions.

Findings

Effective super-Planckian decay constants can be generated without alignment.

Axion mixing mechanisms are common in D-brane models.

Explicit string models demonstrating these mechanisms are constructed.

Abstract

We study the general multi-axion systems, focusing on the possibility of large field inflation driven by axions. We find that through axion mixing from a non-diagonal metric on the moduli space and/or from St\"uckelberg coupling to a U(1) gauge field, an effectively super-Planckian decay constant can be generated without the need of "alignment" in the axion decay constants. We also investigate the consistency conditions related to the gauge symmetries in the multi-axion systems, such as vanishing gauge anomalies and the potential presence of generalized Chern-Simons terms. Our scenario applies generally to field theory models whose axion periodicities are intrinsically sub-Planckian, but it is most naturally realized in string theory. The types of axion mixings invoked in our scenario appear quite commonly in D-brane models, and we present its implementation in type II superstring theory. Explicit stringy models exhibiting all the characteristics of our ideas are constructed within the frameworks of Type IIA intersecting D6-brane models on T6/OR and Type IIB intersecting D7-brane models on Swiss-Cheese Calabi-Yau orientifolds.