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We develop a string-inspired model for particle cosmology, based on a flippedSU(5)$\times$U(1) gauge group formulated in a no-scale supergravity framework.The model realizes Starobinsky-like inflation, which we assume to be followedby strong reheating, with the GUT symmetry being broken subsequently by a light`flaton' field whose decay generates a second stage of reheating. We discussthe production of gravitinos and the non-thermal contribution made by theirdecays to the density of cold dark matter, which is assumed to be provided bythe lightest neutralino. We also discuss the masses of light and heavyneutrinos and leptogenesis. As discussed previously [1], a key r\^ole is playedby a superpotential coupling between the inflaton, matter and GUT Higgs fields,called $\lambda_6$. We scan over possible values of $\lambda_6$, exploring thecorrelations between the possible values of observables. We emphasize that therelease of entropy during the GUT transition allows large regions ofsupersymmetry-breaking parameter space that would otherwise lead to severeoverdensity of dark matter. Furthermore, we find that the Big Bangnucleosynthesis lower limit on the reheating temperature of $\sim 1$ MeVrestricts the supersymmetry-breaking scale to a range ${\cal O}(10)$ TeV thatis consistent with the absence of supersymmetric particles at the LHC.

Superstring-Inspired Particle Cosmology: Inflation, Neutrino Masses, Leptogenesis, Dark Matter & the SUSY Scale