The Search for Fast-Flavor Instability in Magneto-Rotational Core-Collapse Supernovae

At the end of a massive star’s life, the iron core collapses after exceeding the Chandrasekhar limit in a catastrophic core-collapse supernova. These events are primary drivers of nucleosynthesis, progenitors of compact object formation, and hotbeds of high-energy radiation–matter interactions. Magneto-rotational core-collapse supernovae (MR CCSNe) are a higher-energy subset of CCSNe; their energy scales are theorized to be powered by magnetar-scale amplification of the field during collapse. The neutrino plays a key role in critical processes throughout the CCSNe event. Non-linear neutrino-neutrino interactions become more likely with high number densities. Recent work suggests that these non-linear interactions, e.g. the ”fast” flavor instability, can alter the explosion mechanics and nucleosynthesis products in regular CCSNe, but this has not been studied yet in MR CCSNe. Fast flavor instabilities (FFIs), arising from crossings in neutrino angular distributions, are favorable given the high neutrino fluxes produced in MR CCSNe; however, these conditions remain difficult to capture in multidimensional simulations due to the cost of solving the full quantum kinetic equations. As a result, approximate neutrino transport schemes are widely used, yet their performance in predicting FFI conditions remains unclear. In this work, I compare diagnostic results of FFI prediction between a three-dimensional MR CCSNe simulation using the M0 neutrino transport approximation with steady-state Monte Carlo radiation transport snapshots computed with SedonuGR. By analyzing electron-lepton number crossings across both approaches, this study investigates the reliability of transport methods in identifying FFIs in MR CCSNe and situates these results in the broader context of typical CCSNe. Currently, the results are limited by the Monte Carlo statistical noise and no conclusions can yet be made on the development of FFI in MR CCSNe.