Reheating in No-Scale Models of Inflation

Analogously to the suppression of inflaton decays into conformally-coupled scalar fields in the original Starobinsky R + R squared model of inflation, inflaton decays to Standard Model fields are also suppressed in minimal no-scale models of inflation with field space curvature R = 2/3. We study how this suppression can be avoided in generalized no-scale inflationary models. These include models in which the field space curvature R = 2/(3 alpha) with alpha 1 as exemplified by models derived from string theory, as well as models with non-minimal gauge kinetic terms and anomaly-induced couplings. We analyze direct and anomaly-induced inflaton couplings to gauge bosons and gauginos and demonstrate the K"ahler-frame invariance of the physical gauge coupling. We determine the resulting reheating temperatures and the corresponding predictions in the (n s,r) plane. Finally, we consider an R cubed deformation of Starobinsky supergravity, which modifies the inflaton and stabilizer sectors but does not, by itself, generate new tree-level inflaton couplings to visible matter fields.