Dark Matter from Late Invisible Decays to/of Gravitinos
  In this work, we sift a simple supersymmetric framework of late invisible
decays to/of the gravitino. We investigate two cases where the gravitino is the
lightest supersymmetric particle or the next-to-lightest supersymmetric
particle. The next-to-lightest supersymmetric particle decays into two dark
matter candidates and has a long lifetime due to gravitationally suppressed
interactions. However, because of the absence of any hadronic or
electromagnetic products, it satisfies the tight bounds set by big bang
nucleosynthesis and cosmic microwaved background. One or both of the dark
matter candidates produced in invisible decays can contribute to the amount of
dark radiation and suppress perturbations at scales that are being probed by
the galaxy power spectrum and the Lyman-alpha forest data. We show that these
constraints are satisfied in large regions of the parameter space and, as a
result, the late invisible decays to/of the gravitino can be responsible for
the entire dark matter relic abundance.
