Generalized hydrodynamics regime from the thermodynamic bootstrap program

TL;DR

This paper connects the thermodynamic bootstrap program with generalized hydrodynamics in integrable quantum field theories, deriving new axioms and computing correlation functions across different GHD regimes.

Contribution

It introduces a new axiom in the TBP formalism that reproduces GHD correlators and extends calculations to higher particle-hole contributions for diffusive regimes.

Findings

Derived a new TBP axiom matching GHD correlators

Computed higher form factors for diffusive GHD regime

Confirmed agreement with recently conjectured GHD expressions

Abstract

Within the generalized hydrodynamics (GHD) formalism for quantum integrable models, it is possible to compute simple expressions for a number of correlation functions at the Eulerian scale. Specializing to integrable relativistic field theories, we show the same correlators can be computed as a sum over form factors, the GHD regime corresponding to the leading contribution with one particle-hole pair on a finite energy-density background. The thermodynamic bootstrap program (TBP) formalism was recently introduced as an axiomatic approach to computing such finite-energy-density form factors for integrable field theories. We derive a new axiom within the TBP formalism from which we easily recover the predicted GHD Eulerian correlators. We also compute higher form factor contributions, with more particle-hole pairs, within the TBP, allowing for the computation of correlation functions in the diffusive, and beyond, GHD regimes. The two particle-hole form factors agree with expressions recently conjectured within the~GHD.