Thermodynamics in the Sine-Gordon model: the NLIE approach

TL;DR

This paper develops nonlinear integral equations to analyze the thermodynamics of the sine-Gordon model with a chemical potential, enabling precise calculations of local operator expectations and offering insights for experimental cold atom systems.

Contribution

It derives general NLIEs for the sine-Gordon model's thermodynamics with chemical potential, valid at any coupling, and extends them to include momentum conservation effects.

Findings

Derived NLIEs applicable at all coupling strengths.

Enabled computation of local operator expectation values.

Provided theoretical data relevant for cold atomic condensate experiments.

Abstract

In this paper we derive Kl\"umper-Batchelor-Pearce-Destri-de Vega type nonlinear integral equations for describing the thermodynamics in the sine-Gordon model, when a chemical potential coupled to the topological charge is also present in the theory. The equations are valid at any value of the coupling constant and are particularly useful for computing the expectation values of local operators and some currents as functions of the temperature and the chemical potential. The equations are also extended to the case, when an extra term corresponding to the momentum conservation, is added to the thermodynamic potential. The benefits of this description are twofold. On the one hand, it can serve as an appropriate testing ground for other promising theoretical methods, like the method of random surfaces. On the other hand, the efficient computation of vertex operator expectation values, allows one to provide useful theoretical data, for the experimentally measurable coherence factors of a tunnel-coupled cold atomic condensate system.