Speaker
Description
When a neutrino propagates through a medium, the oscillations are modified by forwarding scattering with particles of the medium, which generates a potential in the Hamiltonian. The most famous one is the Wolfenstein potential due to forward scattering with electrons, which leads to the MSW effect. In environments with a high density of neutrinos, such as in supernovae and the early universe, the forward scattering between neutrinos becomes relevant. The neutrino-neutrino interactions lead to a collective non-linear evolution of the neutrino system, which implies a complex evolution equation with non-trivial or easy solutions. In the case of supernova neutrinos, there is not a well-established scenario described by the collective effects. There are analytical solutions for simplified systems, such as an isotropic gas of neutrinos, while others explore numerical solutions for more complicated scenarios. The numerical approach or methods used by different groups are generally not described in detail in the related literature. Unfortunately, there is no free access for the codes used in the numerical approach, which hampers the reproducibility, cross-checks, and further analysis of the results. Therefore, in the present work, we revisit the numerical solutions for the neutrino system evolution when collective effects are accounted for, and moreover, we make available our code as open-source. In its first version, we consider the neutrino evolution inside an isotropic gas of neutrinos. We treat the cases of a mono-energetic gas and the one with a well-defined spectrum, where the latter gives us the well-known collective phenomena of a sharp split in the neutrinos spectra of different flavors.
