Supersymmetry Constraints and String Theory on K3

TL;DR

This paper derives supersymmetry constraints on effective couplings in six-dimensional supergravity and applies these results to obtain exact non-perturbative couplings in type IIB string theory on K3, revealing instanton effects.

Contribution

It introduces supersymmetry non-renormalization conditions for tensor multiplet couplings and extends the understanding of non-perturbative effects in string theory on K3.

Findings

Exact non-perturbative couplings in type IIB on K3 derived

Supersymmetry constraints on 4- and 6-derivative couplings established

Worldsheet instanton contributions captured in moduli-dependent functions

Abstract

We study supervertices in six dimensional (2,0) supergravity theories, and derive supersymmetry non-renormalization conditions on the 4- and 6-derivative four-point couplings of tensor multiplets. As an application, we obtain exact non-perturbative results of such effective couplings in type IIB string theory compactified on K3 surface, extending previous work on type II/heterotic duality. The weak coupling limit thereof, in particular, gives certain integrated four-point functions of half-BPS operators in the nonlinear sigma model on K3 surface, that depend nontrivially on the moduli, and capture worldsheet instanton contributions.