  We consider cosmological solutions in 5d locally supersymmetric theories
including boundary actions, with either opposite tension branes for identical
brane chiralities or equal tension branes for flipped brane chiralities. We
analyse the occurrence of supersymmetry breakdown in both situations. We find
that supersymmetry as seen by a brane observer is broken due to the motion of
the brane in the bulk. When the brane energy-momentum tensor is dominated by
the brane tension, the 4d vacuum energy cosmological constant on the observable
brane is positive and proportional to the inverse square of the brane local
time. We find that the mass splitting within supersymmetric multiplets living
on the brane is of the order of the inverse of the brane local time,
examplifying the tight relation between the vacuum energy scale and the
supersymmetry breaking scale.
