单极子的散射振幅：成对小群和成对螺旋度
Scattering Amplitudes for Monopoles: Pairwise Little Group and Pairwise Helicity
摘要：
在壳方法特别适合于探索电磁带电物体的散射，对于这些物体，没有局部和洛伦兹不变的拉格朗日描述。在本文中，我们将展示如何构建一个洛伦兹不变的S-矩阵的电磁带电粒子的散射，而不必参考狄拉克弦。一个关键因素是我们对庞加莱群的多粒子表示的基本理解的修正。令人惊讶的是，电磁散射的渐近状态转换与一个额外的小群相，与成对的带电粒子和带电粒子。对应的“成对螺旋度”被确定为每个电荷-自旋对的电荷的量子化“叉积”，$e_1 g_2 - e_2 g_1$，并且表示存储在渐近电磁场中的额外角动量。我们定义了一种新的成对旋量-螺旋度变量，它可以作为电磁散射振幅的一个额外的积木。然后，我们构造了最一般的3点S-矩阵元素，以及完整的分波分解的$2\to 2$费米子-S-矩阵。特别是，我们推导出著名的螺旋翻转在最低的分波作为一个简单的后果广义自旋螺旋选择规则，以及较高的分波的全角度依赖。我们的建设提供了一个显着的新成就的壳程序，成功的拉格朗日描述到目前为止失败。
英文摘要：
On-shell methods are particularly suited for exploring the scattering of electrically and magnetically charged objects, for which there is no local and Lorentz invariant Lagrangian description. In this paper we show how to construct a Lorentz-invariant S-matrix for the scattering of electrically and magnetically charged particles, without ever having to refer to a Dirac string. A key ingredient is a revision of our fundamental understanding of multi-particle representations of the Poincaré group. Surprisingly, the asymptotic states for electric-magnetic scattering transform with an additional little group phase, associated with pairs of electrically and magnetically charged particles. The corresponding "pairwise helicity" is identified with the quantized "cross product" of charges, $e_1 g_2 - e_2 g_1$, for every charge-monopole pair, and represents the extra angular momentum stored in the asymptotic electromagnetic field. We define a new kind of pairwise spinor-helicity variable, which serves as an additional building block for electric-magnetic scattering amplitudes. We then construct the most general 3-point S-matrix elements, as well as the full partial wave decomposition for the $2\to 2$ fermion-monopole S-matrix. In particular, we derive the famous helicity flip in the lowest partial wave as a simple consequence of a generalized spin-helicity selection rule, as well as the full angular dependence for the higher partial waves. Our construction provides a significant new achievement for the on-shell program, succeeding where the Lagrangian description has so far failed.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
