Gravity Waves and Gravitino Dark Matter in $\mu$-Hybrid Inflation
  We propose a novel reformulation of supersymmetric (more precisely $\mu$-)
hybrid inflation based on a local U(1) or any suitable extension of the minimal
supersymmetric standard model (MSSM) which also resolves the $\mu$ problem. We
employ a suitable Kahler potential which effectively yields quartic inflation
with non-minimal coupling to gravity. Imposing the gravitino Big Bang
Nucleosynthesis (BBN) constraint on the reheat temperature ($T_r \lesssim 10^6$
GeV) and requiring a neutralino LSP, the tensor to scalar ratio ($r$) has a
lower bound $r \gtrsim 0.004$. The U(1) symmetry breaking scale lies between
$10^8$ and $10^{12}$ GeV. We also discuss a scenario with gravitino dark matter
whose mass is a few GeV.
