Branes and instantons intersecting at angles

TL;DR

This work analyzes a D6 brane together with an euclidean D2 brane instanton intersecting at angles in type IIA, focusing on neutral fermionic zero modes and their saturation. Through a detailed conformal field theory treatment and holomorphy arguments, it shows that such intersecting configurations do not contribute to the low-energy superpotential $W$ when orientifolds or fluxes are absent, aligning with effective field theory expectations. The authors connect these results to dual Type IIB pictures (branes at singularities and magnetized branes) and contrast with scenarios like non-commutative instantons, where tachyons enable recombination and potential non-perturbative effects. The study advances understanding of non-perturbative effects in string compactifications and informs model-building by clarifying which brane-instanton setups can generate superpotential terms.

Abstract

We study in detail the system of D6 branes and euclidean D2-brane instantons intersecting at angles in type IIA string theory. We find that in the absence of orientifolds the system does not contribute to the low energy superpotential, in agreement with expectations based on effective field theory arguments. We also comment on the implications of our results for dual string theory pictures.