Expectation value of composite field $T{\bar T}$ in two-dimensional quantum field theory

TL;DR

This paper derives an exact relation expressing the expectation value of the composite field $T{ar T}$ in terms of the energy-momentum tensor's expectation value in two-dimensional quantum field theory, without assuming integrability.

Contribution

It provides a general, exact formula for the expectation value of the $T{ar T}$ operator in 2D QFT, independent of integrability assumptions.

Findings

Exact relation between $T{ar T}$ and energy-momentum tensor expectation values

Applicable to broad class of 2D quantum field theories

Does not rely on integrability assumptions

Abstract

I show that the expectation value of the composite field $T{\bar T}$, built from the components of the energy-momentum tensor, is expressed exactly through the expectation value of the energy-momentum tensor itself. The relation is derived in two-dimensional quantum field theory under broad assumptions, and does not require integrability.