Fluxbranes: Moduli Stabilisation and Inflation

TL;DR

This paper presents a new moduli stabilization method in string theory that supports fluxbrane inflation, demonstrating compatibility with CMB data and addressing common theoretical challenges like the eta-problem.

Contribution

It introduces a combined F- and D-term moduli stabilization approach using fluxed D7-branes in hierarchically large volume Calabi-Yau compactifications, integrating fluxbrane inflation.

Findings

The inflationary potential is significantly flatter than brane-antibrane models.

CMB and cosmic string constraints are satisfied within the proposed setup.

Potential issues like the eta-problem are discussed and possible solutions are suggested.

Abstract

Fluxbrane inflation is a stringy version of D-term inflation in which two fluxed D7-branes move towards each other until their (relative) gauge flux annihilates. Compared to brane-antibrane inflation, the leading-order inflationary potential of this scenario is much flatter. In the present paper we first discuss a new explicit moduli stabilisation procedure combining the F- and D-term scalar potentials: It is based on fluxed D7-branes in a geometry with three large four-cycles of hierarchically different volumes. Subsequently, we combine this moduli stabilisation with the fluxbrane inflation idea, demonstrating in particular that CMB data (including cosmic string constraints) can be explained within our setup of hierarchical large volume CY compactifications. We also indicate how the eta-problem is expected to re-emerge through higher-order corrections and how it might be overcome by further refinements of our model. Finally, we explain why recently raised concerns about constant FI terms do not affect the consistent, string-derived variant of D-term inflation discussed in this paper.