Matrix Quantum Mechanics and Two-dimensional String Theory in Non-trivial Backgrounds

TL;DR

This paper extends the matrix model approach to 2D string theory in non-trivial backgrounds, demonstrating integrability via Toda Lattice hierarchy and analyzing effects on correlation functions, thermodynamics, and target space structure.

Contribution

It introduces a method to incorporate background perturbations into Matrix Quantum Mechanics, revealing their integrability and enabling detailed analysis of non-trivial 2D string backgrounds.

Findings

Perturbations are integrable and governed by Toda Lattice hierarchy.

Matrix model captures non-trivial background effects in 2D string theory.

Non-perturbative effects are analyzed within the extended framework.

Abstract

String theory is the most promising candidate for the theory unifying all interactions including gravity. It has an extremely difficult dynamics. Therefore, it is useful to study some its simplifications. One of them is non-critical string theory which can be defined in low dimensions. A particular interesting case is 2D string theory. On the one hand, it has a very rich structure and, on the other hand, it is solvable. A complete solution of 2D string theory in the simplest linear dilaton background was obtained using its representation as Matrix Quantum Mechanics. This matrix model provides a very powerful technique and reveals the integrability hidden in the usual CFT formulation. This thesis extends the matrix model description of 2D string theory to non-trivial backgrounds. We show how perturbations changing the background are incorporated into Matrix Quantum Mechanics. The perturbations are integrable and governed by Toda Lattice hierarchy. This integrability is used to extract various information about the perturbed system: correlation functions, thermodynamical behaviour, structure of the target space. The results concerning these and some other issues, like non-perturbative effects in non-critical string theory, are presented in the thesis.