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arXiv quant-ph/0112052quant-ph
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非牛顿力学

Non-Newtonian Mechanics

Giovanni Salesi

摘要:

自旋粒子的经典运动可以不使用格拉斯曼变量或克利福德代数来描述,而只是通过推广通常的无自旋理论。我们只假设关于庞加莱群的不变性;并且只需要线动量和角动量守恒,我们就导出了zitterbewegung:即在牛顿常数项p/m和非牛顿时间振荡类空项中4-速度的分解。因此,自由经典粒子一般不服从惯性原理。在不违反狭义相对论的前提下,只要能量动量沿着质心的世界线运动,超光速运动也是允许的。此外,在不同参考系中测量的持续时间之间存在非线性、非恒定的关系。牛顿力学是作为本理论的一个特例重新获得的:即对于没有zitterbewegung的无自旋系统。引入一个包含4-速度导数的拉格朗日量,我们得到一个新的运动方程,实际上是牛顿定律a=F/m的推广。在满足旋转对称性和重参数化不变性的条件下,我们分别导出了经典自旋矢量和守恒标量哈密顿量。我们还导出了经典的狄拉克自旋,并分析了狄拉克粒子的欧拉-拉格朗日方程的一般解。还研究了自旋系统内禀角动量为零的有趣情况。

英文摘要:

The classical motion of spinning particles can be described without employing Grassmann variables or Clifford algebras, but simply by generalizing the usual spinless theory. We only assume the invariance with respect to the Poincare' group; and only requiring the conservation of the linear and angular momenta we derive the zitterbewegung: namely the decomposition of the 4-velocity in the newtonian constant term p/m and in a non-newtonian time-oscillating spacelike term. Consequently, free classical particles do not obey, in general, the Principle of Inertia. Superluminal motions are also allowed, without violating Special Relativity, provided that the energy-momentum moves along the worldline of the center-of-mass. Moreover, a non-linear, non-constant relation holds between the time durations measured in different reference frames. Newtonian Mechanics is re-obtained as a particular case of the present theory: namely for spinless systems with no zitterbewegung. Introducing a Lagrangian containing also derivatives of the 4-velocity we get a new equation of the motion, actually a generalization of the Newton Law a=F/m. Requiring the rotational symmetry and the reparametrization invariance we derive the classical spin vector and the conserved scalar Hamiltonian, respectively. We derive also the classical Dirac spin and analyze the general solution of the Eulero-Lagrange equation for Dirac particles. The interesting case of spinning systems with zero intrinsic angular momentum is also studied.

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。

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