  We point out that in the early universe, for temperatures in the approximate
interval 175-80 MeV (after the quark-gluon plasma), pions carried a large share
of the entropy and supported the largest inhomogeneities. Thus, we examine the
production of entropy in a pion gas, particularizing to inhomogeneities of the
temperature, for which we benefit from the known thermal conductivity. We
finally put that entropy produced in relaxing such thermal inhomogeneities in
the broad context of this relatively unexplored phase of early-universe
cosmology.
