Higher Derivative F-terms in N=2 Strings

TL;DR

This paper investigates higher derivative F-terms in N=2 string theories, revealing their anomaly equations, connections to c=1 string free energy, and duality relations near singularities involving intersecting D-branes.

Contribution

It introduces a new class of higher derivative F-terms in N=2 strings, analyzes their anomaly equations, and links their singularities to c=1 string and D-brane configurations.

Findings

F_{g,n} terms satisfy anomaly equations similar to F_{g,0}

Leading singularities reproduce c=1 string free energy at arbitrary radius R

Existence of vector gauge fields matching heterotic singularity structure

Abstract

We study a special class of higher derivative F-terms of the form $F_{g,n}W^{2g}(\Pi f)^{n}$ where W is the N=2 gravitational superfield and $\Pi$ is the chiral projector applied to a non-holomorphic function $f$ of the heterotic dilaton vector superfield. We analyze these couplings in the heterotic theory on $K3\times T^2$ , where it is found they satisfy an anomaly equation as the well studied $F_{g,0}$ terms. We recognize that, near a point of SU(2) enhancement, a given generating function of the leading singularity of the $F_{g,n}$ reproduces the free energy of a c=1 string at an arbitrary radius R. According to the N=2 heterotic-type II duality in 4d, we then study these couplings near a conifold singularity, using its local description in terms of intersecting D-5-branes. In this context, it turns out that there exists, among the other states involved, a vector gauge field reproducing the heterotic leading singularity structure.