自旋粒子的运动学理论：两个自旋为1/2的Dirac粒子的相互作用拉格朗日量
Kinematical theory of spinning particles: The interaction Lagrangian for two spin 1/2 Dirac particles
摘要：
基本粒子的概念是基于这样一种观点，即它是一个没有激发态的物理系统，因此粒子的所有可能态都只是其中任何一个的运动学修改。用这种方式，而不是描述粒子属性，它相当于描述连续惯性观察者的集合，这些观察者描述处于相同运动状态的粒子。基本粒子的运动学状态空间是运动学群的齐性空间，通过考虑Galilei群和Poincare群的最大齐性空间，说明了自旋结构与不同自由度的关系。最后，时空对称群的相对论粒子满足狄拉克方程时，量子化，扩大到考虑额外的对称性，如时空膨胀和本地旋转。在此基础上提出了一个相互作用的拉格朗日不变量，并对两个Dirac粒子的复合系统进行了分析。
英文摘要：
The concept of elementary particle rests on the idea that it is a physical system with no excited states, so that all possible states of the particle are just kinematical modifications of any one of them. In this way instead of describing the particle attributes it amounts to describe the collection of consecutive inertial observers who describe the particle in the same kinematical state. The kinematical state space of an elementary particle is a homogeneous space of the kinematical group.By considering the largest homogeneous spaces of both, Galilei and Poincare groups, it is shown how the spin structure is related to the different degrees of freedom. Finally, the spacetime symmetry group of a relativistic particle which satisfies Dirac's equation when quantized, is enlarged to take into account additional symmetries like spacetime dilations and local rotations. An interaction Lagrangian invariant under this enlarged group is proposed and the compound system of two Dirac particles is analyzed.
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