We consider the evolution of baryon number B in the early universe under the influence of rapid sphaleron interactions and show that B will remain nonzero at all times even in the case of B - L = 0. This result arises due to thermal Yukawa interactions that cause nonidentical dispersion relations (thermal masses) for different lepton families. We point out the relevance of our result to the Affleck-Dine type baryogenesis.
Bibliographical noteFunding Information:
K.K. wishes to thank Jim Cline and S.D. wishes to thank H. Murayama and J. March-Russel for useful discussions. This research was supported by the DOE grant DE-FB02-94ER40823, by NSF grant AST 91-20005, by NSERC, KAO:s Presidential Young Investigator Award and by (K.K.) the Finnish Academy.