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arXiv quant-ph/9911046quant-ph
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量子力学中的可调性和边界条件

Orthogonality and Boundary Conditions in Quantum Mechanics

A. Gersten

摘要:

一维粒子态是根据正交条件构造的,不需要边界条件。自由粒子态的构造使用狄拉克的δ函数正交条件。态(二重态)取决于两个量子数:能量和宇称。借助投影算子,粒子被限制在一个约束区域,类似于无限势阱的作用。从所得的过完备基中,只选择相互正交的状态。四个解决方案被发现,对应于不同的非对易哈密顿。用主量子数n和宇称“+”或“-"标记它们的能量本征态。能量本征值仅是n的函数。这四种情况对应于不同的边界条件:(I)波函数在边界上消失,(II)波函数的导数在边界上消失,(III)周期性(对称)边界条件,(IV)周期性(反对称)边界条件。在这四种情况中,只有解(III)构成一个完整的基,在这个意义上,约束区域中的任何函数都可以用它展开,通过将约束区域的边界扩展到无穷远,只有解(III)一致收敛到自由粒子态。与边界条件相比,可扩展性似乎是一个更基本的要求。通过使用投影算子,可以以概念上简单和明确的方式将粒子限制在一个确定的区域内,并且可以编写物理算子,使它们仅作用于受限区域。

英文摘要:

One-dimensional particle states are constructed according to orthogonality conditions, without requiring boundary conditions. Free particle states are constructed using Dirac's delta function orthogonality conditions. The states (doublets) depend on two quantum numbers: energy and parity. With the aid of projection operators the particles are confined to a constrained region, in a way similar to the action of an infinite well potential. From the resulting overcomplete basis only the mutually orthogonal states are selected. Four solutions are found, corresponding to different non-commuting Hamiltonians. Their energy eigenstates are labeled with the main quantum number n and parity "+" or "-". The energy eigenvalues are functions of n only. The four cases correspond to different boundary conditions: (I) the wave function vanishes on the boundary, (II) the derivative of the wavefunction vanishes on the boundary,(III) periodic (symmetric) boundary conditions, (IV) periodic (antisymmetric)boundary conditions . Among the four cases, only solution (III) forms a complete basis in the sense that any function in the constrained region, can be expanded with it. By extending the boundaries of the constrained region to infinity, only solution (III) converges uniformly to the free particle states. Orthogonality seems to be a more basic requirement than boundary conditions. By using projection operators, confinement of the particle to a definite region can be achieved in a conceptually simple and unambiguous way, and physical operators can be written so that they act only in the confined region.

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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