Neutrinos from dense environments : From breakthroughs to new challenges

Neutrinos are elementary particles with mixings. Weakly interacting, they tell us about exploding stars such as core-collapse supernovae, or violent phenomena like binary neutron star mergers. These dense environments produce a huge amount of neutrinos -- about 10⁵⁸ in a few seconds -- which makes the neutrino-neutrino interaction sizeable, and neutrino propagation a non-linear many-body problem.  Such neutrinos are tightly linked to the key questions of heavy elements nucleosynthesis and of the core-collapse supernova explosion mechanism. Their investigation is also crucial for future observations of neutrinos from the next (extra)galactic supernova and of the diffuse supernova neutrino background, whose discovery might be imminent.

            In this talk I will summarize the important progress made in the field over the past two decades, and highlight the perspectives and new challenges. As for the RMP article, I will discuss how I approached the writing and mention the difficulties encountered also because the domain keeps evolving at a fast pace.  I will emphasize what makes the review unique : it gives a comprehensive view of the field gathering together neutrino flavor mechanisms, the main theoretical approaches, observations and emphasizes emerging novel directions e.g. toward quantum computing. Among the personal challenges was to make the field accessible to non-experts.