Abstract
It is shown that, at finite temperature, chiral invariance does not imply that fermion propagators have poles at K2=0. Instead, a zero-momentum fermion has energy K0=M, where M2=g2C(R)T28 and C(R) is the quadratic Casimir of the fermion representation. The dispersion relation for K0 is computed and can be crudely approximated (to within 10%) by K0(M2+K2)12. Applications to high-temperature QCD, SU(2)×U(1), and grand unified theories are discussed.