On the use of statistical concepts in grand unified theories

The study raises the question - whether the use of traditional statistical mechanical concepts is legitimate in the early epochs of the development of the universe (from ≈10-40s after the big bang, until about 10-30s). Several current procedures are examined in detail; the use of the equilibrium notion, the use of Boltzmann-like rate equations, the use of ideas from the theory of phase transitions. It is stressed that from the general viewpoint of statistical mechanics there is no convincing evidence that dynamical systems described by spontaneously broken gauge theories necessarily approach equilibrium. Techniques are suggested whereby this question might be approached.