Time-Scales for Nonlinear Processes in Preheating after Multifield Inflation with Nonminimal Couplings

Understand

We have conducted extensive lattice simulations to study the post-inflation dynamics of multifield models involving nonminimal couplings.

• We explore the parameter dependence of preheating in these models and describe the various time-scales that control such nonlinear processes as energy transfer, re-scattering, and the approach to radiation-domination and thermalization.
• In the limit of large nonminimal couplings ($\xi_I \sim 100$), we find that efficient transfer of energy from the inflaton condensate to radiative degrees of freedom, emergence of a radiation-dominated equation of state, and the onset of thermalization each consistently occur within $N_{\rm reh} \lesssim 3$ $e$-folds after the end of inflation, largely independent of the values of the other couplings in the models.
• The exception is the case of negative ellipticity, in which there is a misalignment between the dominant direction in field-space along which the system evolves and the larger of the nonminimal couplings $\xi_I$.