Duality and Instantons in String Theory

TL;DR

This paper discusses duality tests and instanton effects in string theory, focusing on BPS terms, duality conjectures, and instanton calculus, with detailed examples including heterotic/type-I and type-II dualities.

Contribution

It provides a comprehensive overview of instanton effects and duality tests in string theory, including new rules for instanton calculus and detailed analysis of specific dualities.

Findings

Verified duality conjectures using threshold calculations.

Derived rules for D1-brane and NS5-brane instanton contributions.

Predicted instanton corrections in various string theory models.

Abstract

In these lecture notes duality tests and instanton effects in supersymmetric vacua of string theory are discussed. A broad overview of BPS-saturated terms in the effective actions is first given. Their role in testing the consistency of duality conjectures as well as discovering the rules of instanton calculus in string theory is discussed. The example of heterotic/type-I duality is treated in detail. Thresholds of F^4 and R^4 terms are used to test the duality as well as to derive rules for calculated with D1-brane instantons. We further consider the case of R^2 couplings in N=4 ground-states. Heterotic/type II duality is invoked to predict the heterotic NS5-brane instanton corrections to the R^2 threshold. The R^4 couplings of type-II string theory with maximal supersymmetry are also analysed and the D-instanton contributions are described Other applications and open problems are sketched.