  B and L violating interactions of ordinary particles with their twin
particles from hypothetical mirror world can co-generate baryon asymmetries in
both worlds in comparable amounts, $\Omega'_B/\Omega_B \sim 5$ or so. On the
other hand, the same interactions induce the oscillation phenomena between the
neutral particles of two sectors which convert e.g. mirror neutrons into our
antineutrons. These oscillations are environment dependent and can have
fascinating physical consequences.
