PION POLARIZABILITIES AT FINITE-TEMPERATURE

A first calculation of pion polarizabilities at finite temperature is presented. Compton scattering off a pion is examined in the Nambu-Jona -Lasinio model and an expansion in the inverse number of colors N-c is used. Quark loop, sigma-pole and vector meson contributions to the in variant amplitude are considered. The calculated polarizabilities of t he charged and neutral pions at T = 0 agree fairly well with experimen t. For increasing temperature, the polarizabilities stay fairly consta nt until they diverge at the Mott temperature (T-M = 202.2 MeV), above which the pion can decay into two quarks.