  Cosmological reheating describes the transition of the post-inflationary
universe to a hot and thermal state. In order to shed light on the underlying
dynamics of this process, we propose to quantum-simulate the reheating-like
dynamics of a generic cosmological single-field model in an ultracold Bose gas.
In our setup, the excitations on top of an atomic Bose-Einstein condensate play
the role of the particles produced by the decaying inflaton field after
inflation. Expanding spacetime as well as the background oscillating inflaton
field are mimicked in the non-relativistic limit by a time dependence of the
atomic interactions, which can be tuned experimentally via Feshbach resonances.
As we illustrate by means of classical-statistical simulations for the case of
two spatial dimensions, the dynamics of the atomic system exhibits the
characteristic stages of far-from-equilibrium reheating, including the
amplification of fluctuations via parametric instabilities and the subsequent
turbulent transport of energy towards higher momenta. The transport is governed
by a non-thermal fixed point showing universal self-similar time evolution as
well as a transient regime of prescaling with time-dependent scaling exponents.
While the classical-statistical simulations can capture only the earlier stages
of the dynamics for weak couplings, the proposed experiment has the potential
of exploring the evolution up to late times even beyond the weak coupling
regime.
