Two-dimensional solitons at finite temperature

The partition function of two-dimensional solitons in a heat bath of mesons is worked out to one-loop. For temperatures large compared to the meson ma ss, the free energy is dominated by the meson-soliton bound states and the zero modes, a consequence of Levinson's theorem. Using the Beth-Uhlenbeck f ormula we compare the shift. in the soliton energy to the shift expected in the pole mass at zero momentum using a density expansion. We construct the partition function associated to a fast moving soliton at finite temperatu re, and found that the soliton thermal inertial mass is no longer constrain ed by Poincare symmetry. At finite temperature, the quasiparticle parameter s are process dependent.