  We investigate the critical scaling of the quark propagator of N_f=2 QCD
close to the chiral phase transition at finite temperature. We argue that it is
mandatory to take into account the back-reaction effects of pions and the sigma
onto the quark to observe critical behavior beyond mean field. On condition of
self-consistency of the quark Dyson-Schwinger equation we extract the scaling
behavior for the quark propagator analytically. Crucial in this respect is the
correct pion dispersion relation when the critical temperature is approached
from below. Our results are consistent with the known relations for the quark
condensate and the pion decay constant from universality. We verify the
analytical findings also numerically assuming the critical dispersion relation
for the Goldstone bosons.
