Neutrino Flavor Conversions in High-Density Astrophysical and Cosmological Environments

Despite being a well understood phenomenon in the context of current terrestrial experi-ments, neutrino flavor conversions in dense astrophysical environments probably represent one of the most challenging open problems in neutrino physics. Apart from being theoretically interesting, such a problem has several phenomenological implications in cosmology and in astrophysics, including the primordial nucleosynthesis of light elements abundance and other cosmological observables, nucleosynthesis of heavy nuclei, and the explosion of massive stars. In this review, we briefly sum-marize the state of the art on this topic, focusing on three environments: early Universe, core-collapse supernovae, and compact binary mergers.