Sin-Itiro Tomonaga
Tomonaga, Sin-Itiro (1906-) was a Japanese physicist who shared the 1965 Nobel Prize in physics with American physicists Richard Phillips Feynman and Julian Seymour Schwinger. Working independently of each other, the three scientists developed an improved theory of quantum electrodynamics.
Tomonaga was born in 1906 in Tokyo, but spent most of his early years in Kyoto. He received his undergraduate degree in atomic physics from the Kyoto Imperial University in 1929, and for the next three years he was a research assistant at the university. In 1932, he joined the Institute of Physical and Chemical Research in Tokyo, where he did research on the creation and annihilation of the positron and on the neutron-proton interaction. Between 1937 and 1939, he studied nuclear matter at the University of Leipzig. While there he published a paper on the nucleus of the atom that he submitted to Tokyo Imperial University to earn a doctorate in 1939. In 1941, he was appointed professor of physics at the Tokyo University of Science and Literature. He served as the university's president from 1956 to 1962 and became professor emeritus in 1969.
In the late 1920's, British physicist Paul Adrien Maurice Dirac presented the theory of quantum electrodynamics. In their research during the early 1940's, Tomonaga, Feynman, and Schwinger kept the fundamentals of the theory but improved and expanded upon it by changing the mathematical superstructure. The improved theory enabled scientists to accurately predict the effects of electrically charged particles on each other in a radiation field. Tomonaga's work was significant because he reached his conclusions on the basis of theoretical considerations alone, without benefit of actual experiments. Tomonaga's paper was published in Japan in 1943, but his work was not translated into English until 1948.
In 1951, he was appointed head of the Institute for Scientific Research in Tokyo. He helped establish the Institute for Nuclear Study at the University of Tokyo in 1955. From 1963 to 1969, he was president of the Science Council of Japan and director of the Institute for Optical Research.