Low temperature TBA and GHD for simple integrable QFT

We derive the low temperature thermodynamic equations corrected by virtual processes for integrable QFT on large but finite size space circle. Obtained TBA’s are solved numerically for the sinh-Gordon model. We also derive corresponding Euler scale generalized hydrodynamic (GHD) equations and display them explicitly for small occupation ratio of virtual quasiparticles. The spectrum of velocities for the linear approximation to GHD is numerically calculated.