Richard Easther talks about the era immediately after inflation. If reheating is delayed then the small perturbations in the density of the universe grow, just as they do during matter domination in the late universe. The growth of non-linear structures during this “early dark age” has not been explored in depth until recently and Richard gives an overview of recent work on the topic.

It turns out that the evolution of structures during this era is described mathematically using essentially the same equations as a fuzzy dark matter/ultralight dark matter epoch now. This means all the tools developed for fuzzy dark matter are re-usable in this earlier epoch. In fact, on large enough scales, even a Newtonian N-body code suffices.

There are interesting things to explore in models that have existed since inflation became a topic, one doesn’t need to cook up exotic scenarios, all that is needed is for reheating to not happen instantly. In fact, in units of efoldings, this early matter domination, growth of structures period of time could even last much longer than the late universe matter dominated phase, meaning structures have much longer to grow, and viralise, and accrete more matter – making them a fascinating thing to study.

Richard: https://excursionset.com/about-me

Paper 1: https://arxiv.org/abs/1909.11678
Paper 2: https://arxiv.org/abs/1911.01661
Paper 3: https://arxiv.org/abs/2011.13333
Paper 4: https://arxiv.org/abs/2110.15109