论文标题
中微子快速味道摆。第2部分：碰撞阻尼
Neutrino Fast Flavor Pendulum. Part 2: Collisional Damping
论文作者
论文摘要
在紧凑的天体物理物体中，中微子密度可以很高，以至于中微子 - 中微子中微子的折射可以导致$ν_e\barν_e\barν_e\leftrightArrowν_x\barν_x\ barbarν_x$带有$ x =μ，τ$的快速风味转化，具体取决于中子角度分布。以前，我们已经表明，在同质的轴对称两种味系统中，这些集体溶液类似于陀螺摆。在风味空间中，其偏离弱相互作用方向的偏差是由可变$ \ cos \ vartheta $量化的，该$在$+1 $和$ \ cos \ cos \ cos \ vartheta _ {\ rm min} $之间移动，后者是从线性模式分析中进行的。在下一步中，我们包括风味连贯性的碰撞阻尼，假设所有模式的常见阻尼率$γ$。从经验上讲，我们发现阻尼的垂体运动达到了渐近水平，$ f = a+（1-a）\ cos \ cos \ vartheta _ {\ rm min} $（从数值上讲，$ a \ simeq 0.370 $），不取决于$ \ cos \ cos \ vartheta的细节，除了修复了$ \ vartheta的细节，也不是$γ$。另一方面，即使中微子和抗肿瘤阻尼率之间的微小不对称性也强烈改变了这一图像，甚至可以在原本稳定的系统中实现风味不对称性。
In compact astrophysical objects, the neutrino density can be so high that neutrino-neutrino refraction can lead to fast flavor conversion of the kind $ν_e \barν_e \leftrightarrow ν_x \barν_x$ with $x=μ,τ$, depending on the neutrino angle distribution. Previously, we have shown that in a homogeneous, axisymmetric two-flavor system, these collective solutions evolve in analogy to a gyroscopic pendulum. In flavor space, its deviation from the weak-interaction direction is quantified by a variable $\cos\vartheta$ that moves between $+1$ and $\cos\vartheta_{\rm min}$, the latter following from a linear mode analysis. As a next step, we include collisional damping of flavor coherence, assuming a common damping rate $Γ$ for all modes. Empirically we find that the damped pendular motion reaches an asymptotic level of pair conversion $f=A+(1-A)\cos\vartheta_{\rm min}$ (numerically $A\simeq 0.370$) that does not depend on details of the angular distribution (except for fixing $\cos\vartheta_{\rm min}$), the initial seed, nor $Γ$. On the other hand, even a small asymmetry between the neutrino and antineutrino damping rates strongly changes this picture and can even enable flavor instabilities in otherwise stable systems.
