One-point functions in massive integrable QFT with boundaries

TL;DR

This paper develops a series expansion method for calculating one-point functions in massive integrable quantum field theories with boundaries, validated against numerical methods and relevant to quantum quench studies.

Contribution

It extends the boundary state formalism to finite volume and provides a practical series expansion for one-point functions in boundary integrable QFTs.

Findings

Series expansion matches numerical results in the scaling Lee-Yang model.

Method applicable to quantum quench problems.

Validates boundary form factor approach in finite volume.

Abstract

We consider the expectation value of a local operator on a strip with non-trivial boundaries in 1+1 dimensional massive integrable QFT. Using finite volume regularisation in the crossed channel and extending the boundary state formalism to the finite volume case we give a series expansion for the one-point function in terms of the exact form factors of the theory. The truncated series is compared with the numerical results of the truncated conformal space approach in the scaling Lee-Yang model. We discuss the relevance of our results to quantum quench problems.