On Fluxed Instantons and Moduli Stabilisation in IIB Orientifolds and F-theory

TL;DR

This paper investigates how instanton flux on Euclidean D3-branes can facilitate moduli stabilization in Type IIB orientifolds and F-theory by removing zero modes that hinder stabilization, especially in chiral sectors.

Contribution

It demonstrates that instanton flux can remove zero modes preventing moduli stabilization and proposes an F-theoretic solution involving charged matter fields.

Findings

Instanton flux removes zero modes hindering moduli stabilization.

Fluxed instantons help achieve full moduli stabilization in geometric regimes.

F-theory offers a unique solution via charged matter fields not available at weak coupling.

Abstract

We study the superpotential induced by Euclidean D3-brane instantons carrying instanton flux, with special emphasis on its significance for the stabilisation of Kahler moduli and Neveu-Schwarz axions in Type IIB orientifolds. Quite generally, once a chiral observable sector is included in the compactification, arising on intersecting D7-branes with world-volume flux, resulting charged instanton zero modes prevent a class of instantons from participating in moduli stabilisation. We show that instanton flux on Euclidean D3-branes can remove these extra zero modes and helps in reinstating full moduli stabilisation within a geometric regime. We comment also on the F-theoretic description of this effect of alleviating the general tension between moduli stabilisation and chirality. In addition we propose an alternative solution to this problem based on dressing the instantons with charged matter fields which is unique to F-theory and cannot be realised in the weak coupling limit.