On Factorizable S-matrices, Generalized $T\bar{T}$, and the Hagedorn Transition

Abstract: In this talk, I will consider integrable quantum field theories deformed by some kind of CDD factors. The models involve just one kind of stable particle.  These deformations are related with the $T\bar{T}$ and generalized $T\bar{T}$ deformations.   These models have a factorizable $S$-matrices and their ground state energies $E(R)$ with the spatial  coordinate compactified on a circle  of circumference R can be computed by the Thermodynamic Bethe Ansatz (TBA) equations. I will show that the TBA equations for various models exhibit two real solutions (the primary and secondary branches)  at $R$ greater than a certain critical parameter-dependent value $R^\ast$ (a square-root branching point).  This behavior of $E(R)$ is qualitatively the same as the one for standard $T\bar{T}$ deformations of  local QFT. The singularity signals a Hagedorn behavior of the density of high energy states.  I will finish the talk mentioning several open questions.

HEP - theory

Audience: researchers in the topic

Exact Results on Irrelevant Deformations of QFTs

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