Characterizing the post-inflationary reheating history, Part II: Multiple interacting daughter fields

TL;DR

This paper investigates the post-inflationary reheating process with multiple interacting daughter fields, revealing that energy transfer can exceed 50% and that interactions induce resonances affecting energy distribution.

Contribution

It introduces a detailed lattice simulation study of multi-field reheating with quadratic and scale-free interactions, extending previous single-field models.

Findings

Energy transferred to daughter fields can surpass 50%.

For p ≥ 4, energy is evenly distributed among all fields at late times.

Resonance effects from interactions significantly deplete inflaton energy.

Abstract

We characterize the post-inflationary dynamics of an inflaton $\phi$ coupled to multiple interacting daughter fields $X_n$ ($n=1,\dots N_d$) through quadratic-quadratic interactions $g_n^ 2\phi^2 X_n^2$. We assume a monomial inflaton potential $V(\phi) \propto |\phi|^p$ ($p \geq 2$) around the minimum. By simulating the system in 2+1-dimensional lattices, we study the post-inflationary evolution of the energy distribution and equation of state, from the end of inflation until a stationary regime is achieved. We show that in this scenario, the energy transferred to the daughter field sector can be larger than $50\%$, surpassing this way the upper bound found previously for single daughter field models. In particular, for $p \geq 4$ the energy at very late times is equally distributed between all fields, and only $100/(N_d + 1) \%$ of the energy remains in the inflaton. We also consider scenarios in which the daughter fields have scale-free interactions $\lambda_{nm} X_n^2 X_m^2$, including the case of quartic daughter field self-interactions (for $n=m$). We show that these interactions trigger a resonance process during the non-linear regime, which in the single daughter field case already allows to deplete more than $50\%$ of the energy from the inflaton for $p\geq 4$.