Inconsistency of an inflationary sector coupled only gravitationally

by Daniel Figueroa (EPFL Lausanne)

Monday 12 Nov 2018, 16:30 → 17:30 Europe/Berlin

seminar room 2 (building 2A)

From a model-building perspective, the inflationary sector might very well have no direct couplings to other species, apart from inevitable gravitational interactions. In such a case, a thermal universe can still emerge in the context of gravitational reheating, which introduces an early stiff period in the expansion history of the universe, immediately after inflation. This lead to a significant enhancement of the inflationary gravitational wave (GW) spectrum, making this signal (potentially) observable by LIGO, LISA and other detectors. The very same enhancement leads however to an inconsistency: the energy of the GWs becomes too large, violating standard BBN and CMB bounds on GW backgrounds. Except for unappealing initial radiation sectors, our result is independent of the model parameters, implying that in order to reheat the universe, the inflationary sector must be coupled directly to other particle species.