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Neutrino-Mass-Driven Instabilities as the Earliest Flavor Conversion in Supernovae

Damiano F. G. Fiorillo1,*, Hans-Thomas Janka2, and Georg G. Raffelt3

  • *Contact author: damianofg@gmail.com
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Phys. Rev. Lett. 135, 231003 – Published 2 December, 2025

DOI: https://doi.org/10.1103/jbmx-rbzt

Abstract

Collective neutrino flavor conversions in core-collapse supernovae begin with instabilities, initially triggered when the dominant νe outflow concurs with a small antineutrino flux of opposite lepton number, with ν¯e dominating over ν¯μ. When these “flipped” neutrinos emerge in the energy-integrated angular distribution (angular crossing), they initiate a fast instability. However, before such conditions arise, spectral crossings typically appear within 20 ms of collapse, i.e., local spectral excesses of ν¯e over ν¯μ along some direction. Therefore, postprocessing supernova simulations cannot consistently capture later fast instabilities because the early slow ones have already altered the conditions.

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Phys. Rev. Lett. 135, 231003– Published 2 December, 2025
  • Received 3 August 2025
  • Revised 6 November 2025
  • Accepted 12 November 2025
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