Cosmological baryon asymmetry constraints on extensions of the standard model

The existence of the baryon asymmetry of the Universe puts strong constraints on extensions of the standard model which violate baryon and/or lepton number. Interactions violating baryon number but conserving lepton number in the early universe could wash away any previously established baryon asymmetry. Interactions which violate lepton number separately (as first discussed by Fukugita and Yanagida), with or without associated violation of baryon number, could combine with non-perturbative baryon and lepton number violating electroweak effects to eradicate the cosmological baryon asymmetry. We derive the constraints on any such interaction of arbitrary dimension arising from the persistence of the cosmological baryon asymmetry. We find, in particular, severe constraints on δB≠0 interactions that could mediate n↔n oscillations or δB≠δL proton decay, and on interactions that could violate R parity in supersymmetric models. These constraints severely limit the potential observability of n-n oscillations and R-parity violation in present laboratory experiments.