Energy distribution and equation of state of the early Universe: Matching the end of inflation and the onset of radiation domination
Stefan Antusch, Daniel G. Figueroa, Kenneth Marschall, Francisco Torrentí
Abstract
We study the energy distribution and equation of state of the universe between the end of inflation and the onset of radiation domination (RD), considering observationally consistent single-field inflationary scenarios, with a potential ‘flattening’ at large field values, and a monomial shape V(ϕ)∝|ϕ|p around the origin. As a proxy for (p)reheating, we include a quadratic interaction g2ϕ2X2 between the inflaton ϕ and a light scalar ‘daughter’ field X, with g2>0. We capture the non-perturbative and non-linear nature of the system dynamics with lattice simulations, obtaining that: i) the final energy transferred to X depends only on p, not on g2; ii) the final transfer of energy is always negligible for 2≤p<4, and of order ∼50% for p≥4; iii) the system goes at late times to matter-domination for p=2, and always to RD for p>2. In the latter case we calculate the number of e-folds until RD, significantly reducing the uncertainty in the inflationary observables ns and r.