  Thermal leptogenesis and supergravity are attractive scenarios for physics
beyond the standard model. However, it is well known that the super-weak
interaction of the gravitino often leads to problems with primordial
nucleosynthesis in the standard scenario of matter parity conserving MSSM +
three right-handed neutrinos. We will present and compare two related solutions
to these problems: 1) The conflict between BBN and leptogenesis can be avoided
in presence of a hidden sector with light supersymmetric particles which open
new decay channels for the dangerous long-lived particles. 2) If there is a
condensate in the hidden sector, such additional decay channels can be
alternatively opened by dynamical breaking of matter parity in the hidden
sector.
