Neutrino flavor conversions may dramatically affect the inner working of compact astrophysical objects as well as the synthesis of the heavier elements. We present the first sophisticated numerical solution of the neutrino flavor conversion within a (2+1+1) dimensional setup: we include the advective term in the neutrino equations of motion and track the flavor evolution in two spatial dimensions, one angular variable, and time. Notably, the advective term hinders the development of neutrino pairwise conversions, if the conditions favoring such conversions (i.e., crossings between the angular distributions of $\nu_e$ and $\bar\nu_e$ or a non-negligible flux of neutrinos traveling backward with respect to the main propagation direction) exist for time scales shorter than the typical time scale of the advective term. As a consequence, fast pairwise conversions can only occur when the conditions favoring flavor conversions are self-sustained and global, such as the ones induced by the lepton emission self-sustained asymmetry (LESA) in core-collapse supernovae. Our work highlights the major impact of the dynamical evolution of the neutrino field on the growth of flavor instabilities and the strong interplay between classical and quantum effects. Critical limitations of the linear stability analysis, used to predict neutrino flavor instabilities, are also pointed out.

中文翻译：

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中微子传播阻碍了快速的成对风味转换

中微子风味的转换可能会极大地影响紧凑天体物理物体的内部工作以及较重元素的合成。我们在 (2+1+1) 维设置中提出了中微子风味转换的第一个复杂数值解：我们在中微子运动方程中包含平流项，并在两个空间维度、一个角变量和时间。值得注意的是，平流项会阻碍中微子成对转换的发展，如果有利于这种转换的条件（即 $\nu_e$ 和 $\bar\nu_e$ 的角分布之间的交叉或不可忽略的中微子向后移动的通量相对于主要传播方向）存在于比平流项的典型时间尺度更短的时间尺度。作为结果，快速的成对转换只有在有利于风味转换的条件是自我维持和全局的时才会发生，例如由核心坍缩超新星中的轻子发射自我维持不对称（LESA）引起的条件。我们的工作强调了中微子场的动态演化对风味不稳定性增长的主要影响以及经典效应和量子效应之间的强烈相互作用。还指出了用于预测中微子风味不稳定性的线性稳定性分析的关键局限性。我们的工作强调了中微子场的动态演化对风味不稳定性增长的主要影响以及经典效应和量子效应之间的强烈相互作用。还指出了用于预测中微子风味不稳定性的线性稳定性分析的关键局限性。我们的工作强调了中微子场的动态演化对风味不稳定性增长的主要影响以及经典效应和量子效应之间的强烈相互作用。还指出了用于预测中微子风味不稳定性的线性稳定性分析的关键局限性。