  It is known that the cosmological baryon density (Omega(b)) and dark matter
density (Omega(dm)) have strikingly similar values. However, in most theories
of the early Universe, each density is explained by separate dynamics and
consequently there is no compelling reason for this observation. In this note,
I briefly review a model in which the dark matter possesses a
particle-antiparticle asymmetry. This asymmetry determines both the baryon
asymmetry and strongly affects the dark matter density, thus naturally linking
Omega(b) and Omega(dm). In these models it is shown that sneutrinos can play
the role of such dark matter.
