Characterization of reheating dynamics after inflation

Characterize the dynamics of reheating connecting the end of inflation to radiation domination, including the evolution of the effective equation of state, the duration of reheating, and the underlying decay and interaction processes, to provide a predictive and observationally constrained description of this epoch.

Background

Reheating bridges inflation and the radiation-dominated universe but remains observationally challenging. Its dynamics affect key cosmological quantities such as the number of inflationary e-folds associated with observable scales, the reheating temperature, and the imprint on relic gravitational wave spectra.

A complete description requires integrating the effects of parametric resonance, backreaction, scattering, and thermalization across a range of models and couplings, and connecting these to observables (e.g., CMB constraints, stochastic gravitational waves).

References

Reheating dynamics is one of the important open problems in theoretical and observational cosmology.

— Cosmic Inflation: Background dynamics, Quantum fluctuations and Reheating  (2403.10606 - Mishra, 2024) in Section 7, concluding paragraph

Whether a reheating history can suppress the \chi population while supplying the incident \Psi population used below remains open and requires their coupled production and evolution; no allowed reheating window is established by the rate estimates alone.

— Topological Axi-Higgs Dynamics in Anomalous $U(1)$ Portals  (2609.29207 - Corianò et al., 24 Sep 2026) in Section 7, “Potential-coefficient dependence and an illustrative spectrum”

In particular, it is still unclear how the inflaton's coupling with Standard Model fields affects the universe's evolution during and after inflation.

— Non-minimal Unimodular Inflation  (2608.20095 - Malekpour et al., 20 Aug 2026) in Section 1, Introduction

Such behaviour would supply, within a single framework, the continuous spectrum needed for a finite relaxation rate (point~(i)) and the production, free of exponential suppression, needed to sustain real massive pairs (point~(ii)). Its study in a theoretical framework of an explicit field theory, together with the numerical solution of the closed set eq:closed1 through the reheating epoch, is left to future work.

— Cosmic rate equation and massive particle--antiparticle pair production  (2610.08597 - Xue, 6 Oct 2026) in Section Summary, final paragraph