Multi-instantons in 2d string theory

Fuente: arXiv
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Main Authors: Alexandrov, Sergei, Kaushik, Rishabh
Format: Preprint
Published: 2025
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author Alexandrov, Sergei
Kaushik, Rishabh
author_facet Alexandrov, Sergei
Kaushik, Rishabh
contents Instanton contributions in 2d string theory are known to include subtle numerical factors $ζ_n$ closely related to a contour prescription in multi-instanton string amplitudes. Both ingredients appear to be ambiguous due to a degeneracy between $(1,n)$-ZZ instantons and $n$ (1,1)-ZZ instantons in the linear dilaton background. We resolve this ambiguity using insights from the dual matrix quantum mechanics where the multipliers $ζ_n$ can be derived from an integral representation of the scattering phase and follow from the median resummation prescribed by resurgence theory. We evaluate multi-instanton string amplitudes in the theory compactified on a circle of finite radius for arbitrary number of instantons and show that they reproduce the matrix model predictions provided the Lorentzian contour prescription is used for their evaluation. We also show that the non-perturbative free energy matches the structure of the D-instanton induced string field theory effective action, which suggests the vanishing of contributions from worldsheet topologies of negative Euler number.
format Preprint
id arxiv_https___arxiv_org_abs_2509_03293
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Multi-instantons in 2d string theory
Alexandrov, Sergei
Kaushik, Rishabh
High Energy Physics - Theory
Instanton contributions in 2d string theory are known to include subtle numerical factors $ζ_n$ closely related to a contour prescription in multi-instanton string amplitudes. Both ingredients appear to be ambiguous due to a degeneracy between $(1,n)$-ZZ instantons and $n$ (1,1)-ZZ instantons in the linear dilaton background. We resolve this ambiguity using insights from the dual matrix quantum mechanics where the multipliers $ζ_n$ can be derived from an integral representation of the scattering phase and follow from the median resummation prescribed by resurgence theory. We evaluate multi-instanton string amplitudes in the theory compactified on a circle of finite radius for arbitrary number of instantons and show that they reproduce the matrix model predictions provided the Lorentzian contour prescription is used for their evaluation. We also show that the non-perturbative free energy matches the structure of the D-instanton induced string field theory effective action, which suggests the vanishing of contributions from worldsheet topologies of negative Euler number.
title Multi-instantons in 2d string theory
topic High Energy Physics - Theory
url https://arxiv.org/abs/2509.03293