Form factor expansion for thermal correlators

TL;DR

This paper introduces a new method using multi-dimensional residues to compute finite temperature correlation functions in massive integrable quantum field theories, providing explicit results and examining existing proposals.

Contribution

It develops a novel residue-based approach for form factor expansion of thermal correlators in integrable QFT, especially for theories with diagonal scattering.

Findings

Explicit first terms for diagonal scattering theories

Validation discussion of the LeClair-Mussardo proposal

New regularization technique via finite volume

Abstract

We consider finite temperature correlation functions in massive integrable Quantum Field Theory. Using a regularization by putting the system in finite volume, we develop a novel approach (based on multi-dimensional residues) to the form factor expansion for thermal correlators. The first few terms are obtained explicitly in theories with diagonal scattering. We also discuss the validity of the LeClair-Mussardo proposal.