Baryon number generation in grand unified theories

Grand unified models of elementary particle interactions suggest that there was an early epoch during the Big Bang while the temperature was slightly less than the Planck temperature, during which no known interactions were in thermal equilibrium. This epoch was probably followed by a brief period during which baryon number violating forces were in equilibrium and could have annihilated any previously existing net baryon number. As these forces dropped out of equilibrium, a CP violating component could have generated the observed baryon to entropy ratio of O(10^?9).