Electromagnetic mass difference of pions at low temperature - art. no. 054002

We compute low temperature corrections to the electromagnetic mass differen ce of pious in the chiral limit. The computation is done in a model indepen dent way in the framework of chiral perturbation theory, using the backgrou nd held method and the hard thermal loop approximation. We also generalize at low temperature the sum rule of Das et al. We find that the mass differe nce between the charged and neutral pions decreases at low temperature T wi th respect to the T=0 value. This is so in spite of the fact that charged p articles always get a thermal correction to their masses of order similar t o eT, where e is the gauge coupling constant. Our result can be understood as a consequence of the tendency towards chiral symmetry restoration at fin ite temperature. [S0556-2821(99)00703-1].