BARYON NUMBER VIOLATION AT HIGH-TEMPERATURE IN THE STANDARD MODEL

We explore a suggestion that baryon number violation is unsuppressed in the standard model at high energies and temperatures. We find that baryon number violation is negligible in high energy scattering. On the other hand, in agreement with previous authors, we find that it is indeed unsuppressed at high temperatures. We give simple, qualitative arguments valid even in systems with many degrees of freedom. In particular, we show that there is no extra entropy suppression for production of sphaleron or soliton-antisoliton configurations. Above the weak interaction phase transition, a simple scaling argument gives the rate up to an unknown numerical factor. We also show that passage over the barrier is associated with fermion production. We illustrate the general considerations with a simple model which, for this problem, has features identical to those of the standard model. In this model it is possible to perform many computations explicitly, and a semiclassical analysis may be performed even at high temperature. In addition, we explain why certain criticisms which have been leveled at these ideas are not correct. © 1990.