Prospects of fast flavor neutrino conversion in rotating core-collapse supernovae

TL;DR

This study explores how stellar rotation influences fast flavor conversion of neutrinos in core-collapse supernovae, revealing that rotation promotes conditions conducive to neutrino flavor changes, with implications for supernova explosion dynamics.

Contribution

The paper demonstrates that stellar rotation facilitates fast flavor conversion in supernovae by expanding low-electron-fraction regions and altering neutrino angular distributions, a novel insight into supernova neutrino physics.

Findings

ELN crossings occur preferentially in the equatorial region of rotating CCSNe.

Rotation expands low-electron-fraction regions, promoting ELN crossings.

Neutrino angular distributions are affected by rotation, influencing flavor conversion.

Abstract

There is mounting evidence that neutrinos undergo fast flavor conversion (FFC) in core-collapse supernova (CCSN). In this letter, we investigate the roles of stellar rotation on the occurrence of FFC by carrying out axisymmetric CCSN simulations with full Boltzmann neutrino transport. Our result suggests that electron neutrino lepton number (ELN) angular crossings, which are the necessary and sufficient condition to trigger FFC, preferably occur in the equatorial region for rotating CCSNe. By scrutinizing the neutrino--matter interaction and neutrino radiation field, we find some pieces of evidence that the stellar rotation facilitates the occurrence of FFC. The low-electron-fraction region in the post-shock layer expands by centrifugal force, enhancing the disparity of neutrino absorption between electron-type neutrinos ($\nu_{\rm e}$) and their anti-particles ($\bar{\nu}_{\rm e}$). This has a significant impact on the angular distribution of neutrinos in momentum space, in which $\nu_{\rm e}$ tends to be more isotropic than $\bar{\nu}_{\rm e}$; consequently, ELN crossings emerge. The ELN crossing found in this study is clearly associated with rotation, which motivates further investigation on how the subsequent FFC influences explosion dynamics, nucleosynthesis, and neutrino signals in rotating CCSNe.