N=2 String-String Duality and Holomorphic couplings

TL;DR

This paper reviews N=2 string duality between heterotic and type IIA strings, detailing computations of prepotentials and instanton expansions, and exploring relations with BPS spectral sums.

Contribution

It provides detailed calculations of heterotic prepotentials and F1 functions for specific models, and connects these to Calabi-Yau instanton expansions and BPS spectra.

Findings

Matching heterotic and type IIA instanton expansions

Explicit computation of prepotentials for ST, STU, and STUV models

Insights into BPS spectral sum relations

Abstract

We review aspects of N=2 duality between the heterotic and the type IIA string. After a description of string duality intended for the non-specialist the computation of the heterotic prepotential and the $F_1$ function for the ST, STU and STUV model (V a Wilson line) and the matching with the Calabi-Yau instanton expansions are given in detail. Relations with BPS spectral sums in various connections are pointed out.