  In a general phenomenological model with local supersymmetry, the amount of
massive gravitinos produced in early universe tends to violate the known dark
matter density bound by many orders of magnitude. In the brane world scenario
in Type IIB string theory, we propose a novel way to evade this problem. There,
the standard model of strong and electroweak interactions live inside the
anti-${\rm D3}$-branes ($\overline{\rm D3}$-branes) that span the 3 large
spatial dimensions. Here, the "potential" Goldstino to be absorbed by the
gravitino (to become massive) is the fermion component of the open string
nilpotent superfield $X$ (i.e., $X^2=0$) which is present only inside the
$\overline{\rm D3}$-branes. This non-linear supergravity scenario offers 2 ways
to solve the gravitino problem, with very different particle physics
phenomenologies.
