早稲田大学 · 物理学・天文学
劉佳保教授の研究室では、超新星爆発や二つの中性子星の合体といった極限状態の宇宙環境におけるニュートリノのフラバー変換に注目し、特にニュートリノ同士の自己相互作用と物質との衝突によるデコherenceが引き起こす「衝突的フラバー不安定性(CFI)」を理論的・数値的に解明しています。特に、線形安定性解析と非線形数値シミュレーションを組み合わせ、CFIの成長率を劇的に増幅させる共鳴現象のメカニズムや、空間的均一性の破れやフラワー非対称性が非線形的発展に与える影響を解明しています。この研究は、超新星のエネルギー放出や中性子星合体からのニュートリノ・ガンマ線バーストの理解に貢献するものです。
Figures are computed from collected data and may differ slightly.
Investigations on the resonancelike phenomenon in the collisional flavor instability (CFI) of neutrinos, which were observed in the linear phase recently, are reported. We show that it occurs not only for the isotropy-preserving modes as pointed out in the previous work but also for the isotropy-breaking modes and that it enhances the linear growth rate of the CFI. Employing linear analysis and nonlinear numerical simulations in the two-flavor scheme and under the relaxation approximation for th
Neutrinos are known to undergo flavor conversion processes among the three flavors. The fast flavor conversion (FFC) has been the central piece of flavor conversions taking place in core-collapse supernovae (CCSNe) due to its shorter timescale to the completion of flavor conversion compared to other types of flavor conversion. Although the ordinary collisions between neutrinos and matter were once thought to decohere neutrinos and thus damp flavor conversions, it was recently realized that they
In astrophysical environments such as core-collapse supernovae (CCSNe) and binary neutron star mergers (BNSMs), neutrinos potentially experience substantial flavor mixing due to the refractive effects of neutrino self-interactions. Determining the survival probability of neutrinos in asymptotic states is paramount to incorporating flavor conversions' effects in the theoretical modeling of CCSN and BNSM. Some phenomenological schemes have shown good performance in approximating asymptotic states
Neutrinos are known to undergo flavor conversion among their three flavors. In the theoretical modeling of core-collapse supernova, there has been a great deal of attention to recent discoveries of a new type of neutrino flavor conversions, namely collisional flavor instability (CFI), in which the instability is induced by the flavor-dependent decoherence due to the disparity of neutrino-matter interactions among flavors. In this paper, we study how the appearance of on-shell muons and associate
Investigations on the resonance in the collisional flavor instability (CFI) of neutrinos, which were reported recently, are reported. We show that the resonance occurs not only for the isotropy-preserving modes as pointed out in the previous work but also for the isotropy-breaking modes and that it enhances the growth rate of CFI by orders of magnitude. Employing the linear analysis and nonlinear numerical simulations in the two-flavor scheme and under the relaxation approximation for the collis
Dense neutrino systems, which display collectivity mediated by the weak interaction, have deep parallels with mean-field kinetic systems governed by other fundamental forces. We identify analogues in fast flavor conversion (FFC) of some time-honored nonlinear phenomena in plasmas and self-gravitating systems. We focus in particular on nonlinear Landau damping and collisionless equilibria, which are likely important pieces of the unsolved puzzle of neutrino oscillations in core-collapse supernova
Neutrinos are known to undergo flavor conversion processes among the three flavors. The fast flavor conversion (FFC) has been the central piece of flavor conversions taking place in core-collapse supernovae (CCSNe) due to its shorter timescale to the completion of flavor conversion compared to other types of flavor conversion. Although the ordinary collisions between neutrinos and matter were once thought to decohere neutrinos and thus damp flavor conversions, it was recently realized that they
Impedance analysis is usually used to study the stability of high proportion new energy systems, which needs to know the impedance of the grid-connected converter. However, traditional impedance modeling methods usually simplify the modulation part to unit gain, which affects the modeling accuracy. To address this issue, an experimental and mechanistic hybrid impedance modeling approach for grid-connected converters considering modulation deviation is proposed. Since the deviation value between
In astrophysical environments such as core-collapse supernovae (CCSNe) and binary neutron star mergers (BNSMs), neutrinos potentially experience substantial flavor mixing due to the refractive effects of neutrino self-interactions. Determining the survival probability of neutrinos in asymptotic states is paramount to incorporating flavor conversions' effects in the theoretical modeling of CCSN and BNSM. Some phenomenological schemes have shown good performance in approximating asymptotic states
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