D-effects in Toroidally Compactified Type II String Theory

TL;DR

This paper reviews exact R^4 couplings in maximally supersymmetric type II string theories, highlighting their non-perturbative effects, relations between various branes, and insights into semiclassical calculus in string theory.

Contribution

It provides a comprehensive review of non-perturbative effects and brane relations in R^4 couplings within maximally supersymmetric type II string theories.

Findings

Identification of non-perturbative e^{-1/g} effects from Euclidean D-branes.

Clarification of the relation between Dp-branes and D-(p-2)branes.

Insights into e^{-1/g^2} effects and their connection to instanton calculus.

Abstract

We review exact results obtained for R^4 couplings in maximally supersymmetric type II string theories. These couplings offer a privileged scene to understand the rules of semiclassical calculus in string theory. Upon expansion in weak string coupling, they reveal an infinite sum of non-perturbative e^{-1/g} effects that can be imputed to euclidean D-branes wrapped on cycles of the compactification manifolds. They also shed light on the relation between Dp-branes and D-(p-2)branes, D-strings and (p,q) strings, instanton sums and soliton loops. The latter interpretation takes over in D<=6 in order to account for the e^{-1/g^2} effects, still mysterious from the point of view of instanton calculus. [To appear in the proceedings of the conference "Quantum Aspects of Gauge Theories, Supersymmetry and Unification" held at Neuchatel University, Switzerland, 18-23 September 1997.]