  The similarity of the observed densities of baryons and cold dark matter
suggests that they have a common or related origin. This can be understood in
the context of the MSSM with right-handed (RH) sneutrinos if cold dark matter
is due to a d = 4 flat direction condensate of very weakly coupled RH sneutrino
LSPs and the baryon asymmetry is generated by Affleck-Dine leptogenesis along
the d = 4 (H_{u}L)^{2} flat direction. The correct density of RH sneutrino dark
matter is obtained if the reheating temperature is in the range 10^{6}-10^{8}
GeV. A cold dark matter isocurvature perturbation close to present
observational bounds is likely in the case of inflation driven by a D-term or
by an F-term with suppressed Hubble corrections to the A-terms. An observable
baryon isocurvature perturbation is also possible in the case of D-term
inflation models.
