  We investigate the simplest models where baryon and lepton numbers are
defined as local symmetries spontaneously broken at the low scale and discuss
the implications for cosmology. We define the simplest anomaly-free theory for
spontaneous baryon and lepton number violation which predicts the existence of
lepto-baryons. In this context we study the new sphaleron condition on the
chemical potentials and show the relation between the present baryon asymmetry
and the B-L asymmetry generated in the early universe. The properties of the
cold dark matter candidate for which stability is a natural consequence from
symmetry breaking are briefly discussed.
