Observable r, gravitino dark matter, and non-thermal leptogenesis in no-scale supergravity

We analyse the shifted hybrid inflation in a no-scale supersymmetric SU(5) GUT model which naturally circumvents the monopole problem. The no-scale framework is derivable as the effective field theory of the supersymmetric (SUSY) compactifications of string theory, and yields a flat potential with no anti-de Sitter vacua, resolving the eta problem. The model predicts a scalar spectral tilt n(s) compatible with the most recent measurements by the Planck satellite, while also accommodating large values of the tensor-to-scalar ratio r (similar to 0.0015), potentially measurable by the near-future experiments. Moreover, the proton decay lifetime in the presence of the dimension-5 operators is found to lie above the current limit imposed by the Super-Kamiokande experiment. A realistic scenario of reheating and non-thermal leptogenesis is employed, wherein the reheating temperature T-r lies in the (2 x 10(6) less than or similar to T-r less than or similar to 2 x 10(9)) GeV range, and at the same time realizing gravitino as a viable dark matter (DM) candidate.

Automated summary

In this study, we analyze the shifted hybrid inflation in a no-scale supersymmetric SU(5) GUT model, which effectively avoids the monopole problem. The no-scale framework is derived as the effective field theory of supersymmetric compactifications of string theory, resulting in a flat potential with no anti-de Sitter vacua, resolving the eta problem. The model predicts a scalar spectral tilt (ns) compatible with the latest measurements by the Planck satellite, while also accommodating a large tensor-to-scalar ratio (r) around 0.0015, potentially measurable in near-future experiments. Additionally, the proton decay lifetime in the presence of dimension-5 operators is found to be above the current limit imposed by the Super-Kamiokande experiment. A realistic scenario of reheating and non-thermal leptogenesis is employed, where the reheating temperature (Tr) lies within the (2 x 10(6) less than or similar to Tr less than or similar to 2 x 10(9)) GeV range, while considering the gravitino as a viable dark matter (DM) candidate.