Perturbing Fast Neutrino Flavor Conversion

Abstract

The flavor evolution of neutrinos in dense astrophysical sources, such as core-collapse supernovae or compact binary mergers, is non-linear due to the coherent forward scattering of neutrinos among themselves. Recent work in this context has been addressed to figure out whether flavor equipartition could be a generic flavor outcome of fast flavor conversion. We investigate the flavor conversion physics injecting random perturbations in the neutrino field in two simulation setups: 1. a spherically symmetric simulation shell without periodic boundaries, with angular distributions evolving dynamically thanks to non-forward scatterings of neutrinos with the background medium, and neutrino advection; 2. a periodic simulation shell, with angular distributions of neutrinos defined a priori and neutrino advection. We find that, independent of the exact initial flavor configuration and type of perturbations, flavor equipartition is generally achieved in the system with periodic boundaries; in this case, perturbations aid the diffusion of flavor structures to smaller and smaller scales. However, flavor equipartition is not a general outcome in the simulation shell without periodic boundaries, where the inhomogeneities induced perturbing the neutrino field affect the flavor evolution, but do not facilitate the diffusion of flavor waves. This work highlights the importance of the choice of the simulation boundary conditions in the exploration of fast flavor conversion physics.

24 pages, including 11 figures and 2 appendices. Minor changes, matches version accepted for publication in JCAP. Supplemental material is available at this link: https://sid.erda.dk/share_redirect/CjZUbh90L0/index.html

References in corpus (10)

• Simulation of Coherent Non-Linear Neutrino Flavor Transformation in the Supernova Environment I: Correlated Neutrino Trajectories
• Fast Pairwise Conversion of Supernova Neutrinos: A Dispersion-Relation Approach
• The multi-angle instability in dense neutrino systems
• Neutrino emission characteristics and detection opportunities based on three-dimensional supernova simulations
• Imprints of neutrino-pair flavor conversions on nucleosynthesis in ejecta from neutron-star merger remnants
• Anisotropic emission of neutrino and gravitational-wave signals from rapidly rotating core-collapse supernovae
• Fast flavor oscillations in dense neutrino media with collisions
• Collective fast neutrino flavor conversions in a 1D box: Initial condition and long-term evolution
• A change of direction in pairwise neutrino conversion physics: The effect of collisions
• Neutrino Fast Flavor Pendulum. Part 2: Collisional Damping