Instanton Induced Open String Superpotentials and Branes at Singularities

TL;DR

This paper explores how Euclidean E3-branes induce non-perturbative superpotentials in D3/D7-brane systems at orbifold singularities, revealing new couplings and instanton effects relevant for string phenomenology.

Contribution

It provides a detailed analysis of instanton-induced superpotentials, including novel multi-instanton effects and their phenomenological implications in orbifold singularities.

Findings

E3-instantons generate phenomenologically relevant couplings like μ-terms and Yukawa interactions.

Combination of E3-instantons with gauge instantons yields new multi-instanton superpotential contributions.

Non-SUSY singularities exhibit non-perturbative scalar couplings from E3-instantons.

Abstract

We study different aspects of the non-perturbative superpotentials induced by Euclidean E3-branes on systems of D3/D7-branes located at Abelian orbifold singularities. We discuss in detail how the induced couplings are consistent with the U(1) symmetries carried by the D3/D7-branes. We construct different compact and non-compact examples, and show phenomenologically relevant couplings like $\mu$-terms or certain Yukawa couplings generated by these E3 instantons. Some other novel effects are described. We show an example where E3-instantons combine with standard gauge instantons to yield new multi-instanton effects contributing to superpotential, along the lines of ref.\cite{geu}. In the case of non-SUSY $Z_N$ tachyon-free singularities it is shown how E3-instantons give rise to non perturbative scalar couplings including exponentially suppressed scalar bilinears.