In my talk I will discuss several aspects of the "primordial dark age" of the universe: the era connecting the end of inflation with the later thermal evolution. I will first review (p)reheating after inflation. I will then show how numerical simulations allow us to characterize the long-term evolution of the energy distribution and equation of state during reheating, and to eliminate the uncertainty in theoretical predictions for inflationary observables. I will also present CosmoLattice: a code for lattice simulations of classical field theories in an expanding universe. The code is capable of simulating scalars, gauge fields and tensor perturbations (gravitational waves), and is currently being used in the study of relevant early universe scenarios. I will discuss about its basic features and future updates.
IFIC seminar organizers. This IFIC Seminar has received funding/support from the GVA Research Project "Understanding non-perturbativie Phenomena in fundamental physics" (PROMETEO/2021/083).