Thermodynamic Bethe Ansatz past turning points: the (elliptic) sinh-Gordon model

We analyze the Thermodynamic Bethe Ansatz (TBA) for various integrable S-matrices in the context of generalized T (T) over bar deformations. We focus on the sinh-Gordon model and its elliptic deformation in both its fermionic and bosonic realizations. We confirm that the determining factor for a turning point in the TBA, interpreted as a finite Hagedorn temperature, is the difference between the number of bound states and resonances in the theory. Implementing the numerical pseudo-arclength continuation method, we are able to follow the solutions to the TBA equations past the turning point all the way to the ultraviolet regime. We find that for any number k of resonances the pair of complex conjugate solutions below the turning point is such that the effective central charge is minimized. As k -> infinity the UV effective central charge goes to zero as in the elliptic sinh-Gordon model. Finally we uncover a new family of UV complete integrable theories defined by the bosonic counterparts of the S-matrices describing the Phi(1,3) integrable deformation of non-unitary minimal models M-2(,2n+3).

Automated summary

In this paper, we analyze the Thermodynamic Bethe Ansatz (TBA) for various integrable S-matrices in the context of generalized T(T)bar deformations, with a focus on the sinh-Gordon model and its elliptic deformation. We confirm that the determining factor for a turning point in the TBA is the difference between the number of bound states and resonances in the theory. By implementing a numerical method, we are able to follow the solutions to the TBA equations to the ultraviolet regime and find that the effective central charge tends to zero as the number of resonances approaches infinity. Additionally, we uncover a new family of UV complete integrable theories defined by the bosonic counterparts of the S-matrices.