Gravitational wave signals and cosmological consequences of gravitational reheating

Understand

Reheating after inflation can proceed even if the inflaton couples to Standard Model (SM) particles only gravitationally.

• However, particle production during the transition between de-Sitter expansion and a decelerating Universe is rather inefficient and the necessity to recover the visible Universe leads to a non-standard cosmological evolution initially dominated by remnants of the inflaton field.
• We remain agnostic to the specific dynamics of the inflaton field and discuss a generic scenario in which its remnants behave as a perfect fluid with a general barotropic parameter $w$.
• Using CMB and BBN constraints we derive the allowed range of inflationary scales.