Normalization of D-instanton Amplitudes

TL;DR

This paper demonstrates how string field theory and world-sheet methods can determine the normalization of D-instanton amplitudes, resolving previous ambiguities and aligning with matrix model results in two-dimensional string theory.

Contribution

It shows that combining string field theory with world-sheet descriptions can fix the normalization constant of D-instanton amplitudes, which was previously undetermined.

Findings

Normalization constant fixed using combined methods

Results agree with matrix model in 2D string theory

Clarifies infrared divergence resolution in D-instanton calculations

Abstract

D-instanton amplitudes suffer from various infrared divergences associated with tachyonic or massless open string modes, leading to ambiguous contribution to string amplitudes. It has been shown previously that string field theory can resolve these ambiguities and lead to unambiguous expressions for D-instanton contributions to string amplitudes, except for an overall normalization constant that remains undetermined. In this paper we show that string field theory, together with the world-sheet description of the amplitudes, can also fix this normalization constant. We apply our analysis to the special case of two dimensional string theory, obtaining results in agreement with the matrix model results obtained by Balthazar, Rodriguez and Yin.