简介

发现

英语介绍

简介

Julian Schwinger (12th,February,1918—1994)

朱利安·施温格，美国物理学家。与费恩曼（Richard Phillips Feynman, 1918-1988）和朝永振一郎（Sin-itiro Tomonaga, 1906-1979）一起，因在量子电动力学方面所做的对基本粒子物理学具有深刻影响的基础性研究，共同分享了1965年度诺贝尔物理学奖。

20世纪20年代建立的处理电子与电磁辐射相互作用的量子场论成功地描述了原子内光的辐射和吸收、喇曼效应、康普顿效应、光电效应以及正负电子对的产生，但是，这种场论存在“发散”困难，即在许多计算中都会得到无穷大这一荒谬的结果。朝永振一郎（左图）和施温格（右图）分别提出，要消除“发散”困难，就应该考虑电子的质量会因电子和场的相互作用而改变，必须进行“重整化”。“重整化”方法能够很好地解释兰姆位移和电子的反常磁矩。

费恩曼（左图）在研究量子力学基本问题的过程中，运用作用量的表现形式，建立了量子力学的路径积分方法，并用它重新写出了整个量子电动力学，使之具有相对论协变性。他把基本过程看作是粒子从一点到另一点的传播，并用简单图形来描绘基本粒子之间的相互作用，这就是粒子物理学家十分熟悉的费恩曼图。

发现

费恩曼、施温格和朝永振一郎彼此独立地创建了物理学中也许是最近乎完美的理论，他们三人提出了各自独特的想法，却得出了一致的结论。他们提出的量子电动力学理论正确地描述了电子、光子及其相互作用，经受住了十分精确的实验检验，成为描述电磁相互作用的基本理论。

英语介绍

Julian Schwinger was born on 12th February 1918 in New York City. The principal direction of his life was fixed at an early age by an intense awareness of physics, and its study became an all-engrossing activity. To judge by a first publication, he debuted as a professional physicist at the age of sixteen. He was allowed to progress rapidly through the public school system of New York City. Through the kind interest of some friends, and especially I.I. Rabi of Columbia University, he transferred to that institution, where he completed his college education. Although his thesis had been written some two or three years earlier, it was in 1939 that he received the Ph.D. degree.

For the next two years he was at the University of California, Berkeley, first as a National Research Fellow and then as assistant to J.R. Oppenheimer. The outbreak of the Pacific war found Schwinger as an Instructor, teaching elementary physics to engineering students at Purdue University.

War activities were largely confined to the Radiation Laboratory at the Massachusetts Institute of Technology in Cambridge. Being a confirmed solitary worker, he became the night research staff. More scientific influences were also at work. He first approached electromagnetic radar problems as a nuclear physicist, but soon began to think of nuclear physics in the language of electrical engineering. That would eventually emerge as the effective range formulation of nuclear scattering. Then, being conscious of the large microwave powers available, Schwinger began to think about electron accelerators, which led to the question of radiation by electrons in magnetic fields. In studying the latter problem he was reminded, at the classical level, that the reaction of the electron's field alters the properties of the particle, including its mass. This would be significant in the intensive developments of quantum electrodynamics, which were soon to follow.

With the termination of the war Dr. Schwinger accepted an appointment as Associate Professor at Harvard University. Two years later he became full Professor. That was also the year of his marriage to Clarice Carrol of Boston.

In subsequent years, he worked in a number of directions, but there was a pattern of concentration on general theoretical questions rather than specific problems of immediate experimental concern, which were nearer to the center ot hls earlier work. A speculative approach to physics has its dangers, but it can have its rewards. Schwinger was particularly pleased by an anticipation, early in 1957, of the existence of two different neutrinos associated, respectively, with the electron and the muon. This has been confirmed experimentally only rather recently. A related and somewhat earlier speculation, that all weak interactions are transmitted by heavy, charged, unit-spin particles still awaits a decisive experimental test. Schwinger's policy of finding theoretical virtues in experimentally unknown particles has culminated recently in a revived concern with magnetically charged particles, which may also be involved in the understanding of strong interactions.

In later years, Schwinger has followed his own advice about the practical importance of a phenomenological theory of particles. He has invented and systematically developed source theory, which deals uniformly with strongly interacting particles, photons, and gravitons, thus providing a general approach to all physical phenomena. This work has been described in two volumes published under the title "Particles, Sources, and Fields".

Awards and other honors include the first Einstein Prize (1951), the U.S. National Medal of Science (1964), honorary D.Sc. degrees from Purdue University (1961) and Harvard University (1962), and the Nature of Light Award of the U.S. National Academy of Sciences (1949). Prof. Schwinger is a member of the latter body, and a sponsor of the Bulletin of the Atomic Scientists.