Two-dimensional massive integrable models on a torus

The finite-volume thermodynamics of a massive integrable QFT is described in terms of a grand canonical ensemble of loops immersed in a torus and interacting through scattering factors associated with their intersections. The path integral of the loops is evaluated explicitly after decoupling the pairwise interactions by a Hubbard-Stratonovich transformation. The HS fields are holomorphic fields depending on the rapidity and can be expanded in elementary oscillators. The torus partition function is expressed as certain expectation value in the Fock space of these oscillators. In the limit where one of the periods of the torus becomes asymptotically large, the effective field theory becomes mean field type. The mean field describes the infinite-volume thermodynamics which is solved by the Thermodynamical Bethe Ansatz.

Automated summary

The finite-volume thermodynamics of a massive integrable QFT is described in this article, which involves a grand canonical ensemble of loops interacting through scattering factors associated with their intersections. The evaluation of the path integral is done after decoupling the pairwise interactions using a Hubbard-Stratonovich transformation. In the limit of a large torus period, the effective field theory becomes mean field type and is solved using the Thermodynamical Bethe Ansatz.