The Use of the Proper Time in Quantum Electrodynamics I
The Use of the Proper Time in Quantum Electrodynamics I
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量子电动力学中本征时间的运用 I
DOI：
10.1143/ptp/5.1.82
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发表时间：
1950
影响因子：
--
通讯作者：
Y. Nambu
中科院分区：
文献类型：
--
作者：
Y. Nambu
费曼提出的量子电动力学的时空方法，似乎为这一物理学领域提供了一个非常吸引人和有用的想法。他巧妙的方法确实很有吸引力，不仅因为它的直观程序使人能够向自己描绘基本粒子的复杂相互作用，它的易用性和相对论的正确性，人们可以用它来计算必要的矩阵元素或跃迁概率，还因为它的思维方式乍看起来有点奇怪，抵制我们习惯于因果定律的思维。根据新的观点，一个人从四个维度整体地看待世界。将在这个剧场上演的一个现象，现在已经预先详细地展示了，从远古的过去到最终的未来，我们可以一目了然地研究它的全部。时间本身失去了作为现象发展的指示器的意义；在时间的溪流中，既有向下流动的粒子，也有向上流动的粒子；可能偶尔发生的对的最终产生和消灭，不是创造或消灭，而只是运动粒子从过去到未来，或从未来到过去的方向的改变；按照通常的观点，虚拟对注定只存在有限的时间间隔，也可以被视为在四维空间的封闭轨道上循环的单个粒子；因此，一个真正的粒子是这样一个粒子，它的轨道不是闭合的，而是到达无穷大。在这种观点下，既包括实粒子又包括虚粒子的规定粒子数的状态并不完全对应于通常意义上的四维态，即由满足含时薛定谔方程的波函数表示的状态。但前者是后者的一部分，在后者中可以允许出现任意数量的虚拟粒子t9。为了得到实际状态的概念，我们必须对虚粒子的数目的所有可能性求和。现在意义上的四维态的解释也变得与传统的解释有所不同，因为它给出了跃迁！
The space-time approach to quantum electrodynamics, as has been developed by Feynman,I> seems to offer a very attractive and useful idea to this domain of physics. His ingenious method is indeed attractive, not only because of its 'intuitive procedure which enables one to picture to oneself the complicated interactions of elementary particles, its ease and relativistic correctness with which one can calculate the necessary matrix elements or transition probabilities, but also because of its way of thinking which seems somewhat strange at first look and resists our minds that are accustomed to causal laws. According t(fthe new standpoint, one looks upon the world in its four-dimensional entirety. A phenomenon that wiII come into play in this theatre is now laid out beforehand in full detail from immemorial past to ultimate future and one investigates the whole of it at glance. The time itself loses sense as the indicator of the development of phenomena; there are particles which flow down as well as up the stream of time; theeventual creation and annihilation of pairs that may occur now and then, is no creation nor annihilation, but only a change of directions of moving particles, from past to future, or from future to past; a virtual pair, which, according to the ordinary view, is foredoomed to exist only for a limited interval of time, may also be regarded as a single particle that is circulating round a closed orbit in the four-dimensional theatre; a real particle is then a particle whose orbit is not closed but reaches to infinity ... In such a view, a state with prescribed number of particles incluliing real as well as virtual does not exactly correspond to a four-dimensional state in the ordinary sense, that is, a state represented by the wave function satisfying the time dependent Schroedinger equation. But the former is rather a part of the latter in which any number of viltual particles may be allowed t9 occur. To obtain an idea of the actual state we shall have to sum over all possibilities as to the number of virtual particles. The interpretation of the four-dimensional state in the present sense becomes also somewhat different from the conventional one as giving the transition pro!.