Sin-Itiro Tomonaga The Nobel Prize in Physics 1965


Japanese theoretical physicist Sin-Itiro Tomonaga resolved key problems with the theory of quantum electrodynamics (QED) developed by Paul Dirac in the late 1920s through the use of a mathematical technique he referred to as renormalization. Tomonaga’s work did not change the basic physical foundation of Dirac’s theory, which described the relationships between electrically charged particles and the electromagnetic field, but rather refined QED in order to make it consistent with the theory of special relativity and to show that the theory agrees quantitatively with results obtained experimentally to a great degree of accuracy. In 1965, Tomonaga received a portion of the Nobel Prize in Physics for his contributions to quantum electrodynamics. He shared the award with American physicists Julian Schwinger and Richard Feynman, who similarly worked out the difficulties inherent in QED as described by Dirac at about the same time as Tomonaga, albeit through different means.

The son of a philosophy professor, Tomonaga was born in Tokyo in 1906. He spent his early childhood there, but in 1913 his family relocated to Kyoto. Tomonaga attended Kyoto Imperial University (where his father taught), earning the Japanese equivalent to a bachelor’s degree in physics in 1929. He then began graduate studies. At the time physics was being revolutionized by such scientists as Dirac, Werner Heisenberg, and Wolfgang Pauli, who were forming the backbone of quantum mechanics. At first Tomonaga carried out graduate research in the laboratory of Kajuro Tomaki in Kyoto, but later he transferred to the Science Research Institute in Tokyo, where he worked under Yoshio Nishina. He focused on the nascent field of quantum electrodynamics, which would retain his attention throughout his career.

In the late 1930s, Tomonaga had the opportunity to visit the University of Leipzig. In Germany he worked with Heisenberg’s group and produced a paper on the nucleus of the atom that served as his dissertation when he returned to Japan in 1939 and received his doctoral degree. In 1940 he married Ryoko Sekiguchi, with whom he would have three children, and in 1941 he accepted a physics professorship at Bunrika University, which later became incorporated into the Tokyo University of Education. He taught and held various departmental posts until 1956, when he became university president.

Shortly after he joined Bunrika University, Tomonaga began his groundbreaking work in quantum electrodynamics. However, due to World War II, he was not in contact with western physicists. Tomonaga’s key papers describing his use of renormalization and his adaptation of QED theory appeared in Japan in 1943, but were not translated into English until 1948. By that time, Schwinger and Feynman had independently completed similar work. The American physicists, however, based their approaches partly on experiments, whereas Tomonaga considered QED from a purely theoretical standpoint. Together their work saved QED, which some scientists had contemplated abandoning because of the incongruity between theoretical predictions and experimental findings.

Following the war, Tomonaga’s contributions to quantum electrodynamics gained him wide recognition. In 1949, he went to Princeton University for two years as a visiting scholar, then returned to his position in Japan.

Tomonaga stepped down as president of Tokyo University in 1962, but was appointed director of the school’s Institute of Optical Research the following year. Also in 1963 he became president of the Science Council of Japan. In 1969 he retired from both posts. Ten years later, on July 8, 1979, Tomonaga died in Tokyo. The great physicist received many honors over the course of his career. In addition to the Nobel Prize, he accepted the Japan Academy Prize, the Order of Culture of Japan and the Lomonosov Gold Medal, bestowed by the Russian Academy of Sciences. Throughout his life, Tomonaga dedicated himself to stemming the proliferation of nuclear weapons while encouraging the use of nuclear energy for peaceful purposes. His efforts proved critical in the foundation of the University of Tokyo’s Institute for Nuclear Studies
Sin-Itiro Tomonaga was born in Tokyo, Japan, on March 31, 1906, the eldest son of Sanjuro Tomonaga and Hide Tomonaga. In 1913 his family moved to Kyoto when his father was appointed a professor of philosophy at Kyoto Imperial University. From that time he was brought up in Kyoto. He is a graduate of the Third Higher School, Kyoto, a renowned senior high school which has educated a number of leading personalities in prewarJapan. Tomonaga completed work for Rigakushi (bachelor's degree) in physics at Kyoto Imperial University in 1929, with one of his intimate friends. Dr. Hideki Yukawa, Nobel laureate. He was engaged in graduate work for three years at the same university and was then appointed a research associate by Dr. Yoshio Nishina at the Institute of Physical and Chemical Research, Tokyo, where he started to work in a newly developed frontier of theoretical physics quantum electrodynamics - under the guidance of Dr. Nishina. His paper on the photoelectric pair creation is well-known. Tomonaga stayed in Leipzig, Germany, from 1937 to 1939, to study nuclear physics and the quantum field theory in collaboration with the theoretical group of Dr. W. Heisenberg, where he published a paper "Innere Reibung und W?rmeleitf?higkeit der Kernmaterie", which was chosen as the thesis for Rigakuhakushi (Doctor of Science) at Tokyo Imperial University in December,1939.

In 1940, Dr. Tomonaga directed his attention to the meson theory and developed the intermediate coupling theory in order to clarify the structure of the meson cloud around the nucleon. He joined the faculty of Tokyo Bunrika University (which was absorbed into the Tokyo University of Education in 1949*) as Professor of Physics in 1941. It was in 1942 when he first proposed the covariant formulation of the quantum field theory in which the concept of the quantum state was generalized so as to be relativistically covariant. During the Second World War, Dr. Tomonaga was interested in developing a theory of microwave systems. He solved the motion of electrons in the magnetron and also developed a unified theory of the systems consisting of wave guides and cavity resonators.

As soon as the War was over, Tomonaga came back to academic research again with a programme in which he was first to summarize and extend the intermediate coupling theory and secondly to apply the covariant field theory to actual physical systems. His aim was to investigate the nature of field reaction in the meson theory as well as in quantum electrodynamics. He was confident, prior to the Lamb-Rutherford experiment, by means of a model calculation that divergence difficulty in quantumelectrodynamics could be overcome simply by handling the infinite mass and charge due to field reactions in some way or another. It was only a step further for him to develop the renormalization theory with covariant formalism in his right hand and experimental support in his left. Dr. Tomonaga was invited to the Institute for Advanced Study, Princeton, in 1949 where he was engaged in the investigation of a one-dimensional fermion system. Thus he first succeeded in clarifying the nature of collective oscillations of a quantum-mechanical many-body system and opened a new frontier of theoretical physics, modern many-body problem. In 1955, he published an elementary theory of quantum mechanical collective motions. Dr. Tomonaga took the leadership in establishing the Institute for Nuclear Study, University of Tokyo, in 1955. From 1956 to 1962 he was appointed President of the Tokyo University of Education and since 1963 he has been President of the Science Council of Japan and Director of the Institute for Optical Research, Tokyo University of Education. He occupies an important position in various governmental committees for scientific research and policymaking. Tomonaga's honours and awards include the Japan Academy Prize (1948);

the Order of Culture (1952); the Lomonosov Medal, U.S.S.R. (1964). Dr. Tomonaga is a member of the Japan Academy, the Deutsche Akademie der Naturforscher "Leopoldina" and a foreign member of the Royal Swedish Academy of Science. He is a corresponding member of the Bayerische Akademie der Wissenschaften and a foreign associate of the National Academy of Science of U.S.A. Tomonaga has published widely in scientific journals on such subjects as quantum electrodynamics, the meson theory, nuclear physics, cosmic rays, and the many-body problem. His book, "Quantum Mechanics", was published in 1949 and translated into English in 1963. Tomonaga was married in 1940 to Ryoko Sekiguchi, daughter of Dr. K. Sekiguchi, the former Director of the Tokyo Metropolitan Observatory. They have two sons, Atsushi and Makoto and one daughter. Their daughter was married in 1965 to Dr. Y. Nagashima, research associate of the Physics Department, University of Rochester

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