• Dr. Sin-Itiro Tomonaga


    Biography

    1926-1929 Department of Physics, Faculty of Science, Kyoto Imperial University (Dr. Hideki Yukawa was a classmate)
    1939 Graduated with Ph. D. in Science from Kyoto Imperial University for research on nuclear materials
    1941 Became Professor of Tokyo University of Science and Literature
    1949 Became Professor of Tokyo University of Education
    1956-1962 President of Tokyo University of Education
    1963-1969 President of Science Council of Japan, Director of Institute of Optical Research, Tokyo University of Education
    1969 Became Professor Emeritus of Tokyo University of Education
    1979 Died on July 8.

    Awards

    1939 Asahi Press Award: “Development of the mesonic theory and the super-many-time theory” 1948 Japan Academy Prize: “Oscillation mechanism of magnetron” 1951 Selected as a member of Japan Academy 1963-1969 President of Science Council of Japan 1964 Lomonosov Medal from the Academy of USSR for his contribution to physics 1965 Nobel Prize for Physics 1976 Grand Cordon of the Order of the Sacred Treasure

    Research Works

    Dr. Tomonaga contributed to a broad range of theoretical physics, but his main works can be classified into the following four:

    1) The super-many-time theory and renormalization theory

    Quantum field theory, which explains the behavior of elementary particles, had a flaw that the relation of this theory with the theory of relativity was not entireily clear. Dr. Tomonaga overcame this difficulty by introducing the super-many-time theory based on the idea that each point of space has its own specific time.
    Furthermore, the field theory of the electron and electro-magnetic fields, quantum electrodynamics, had an inherent contradiction that all calculated physical quantities became infinite. However, the super-many-time theory showed that each infinite term could be regarded as a correction to the mass and charge of electrons.
    By renormalizing these infinities into the mass and charge of the electron, all physical quantities become finite, and thus the theory can explain experiments well. This is the renormalization theory of Dr. Tomonaga.

    2) The theory of collective motions

    Macroscopic matter contains approximately 1022 atoms (??) per 1 cm3, and these atoms exhibit not only random but also organized motion as a whole. These are called collective motions of many-body systems (e.g., acoustic waves in matter). Dr. Tomonaga established a general method for dealing with many-body systems which can separate collective motions from random motions of atoms. This method is currently applied in many areas of theoretical physics.

    3) The mesonic theory

    According to the meson theory of Dr. H. Yukawa, nucleons (protons and neutrons) in the atomic nuclei interact with a strong force called the nuclear force via mesons. Dr. Tomonaga clarified the physical meaning of the meson theory by analyzing the mathematical structures of the theory, such as problems concerning the "field reaction" which mesons give to nucleons, and the method of intermediate coupling for less strong mutual interactions.

    4) Magnetron and stereo-circuits

    The theoretical work on the oscillation mechanism of the magnetron is very famous as an applied physics work done during the war. In particular, the theory of microwave stereo-circuits, which was constructed by analogy with an atomic nucleus reaction theory, put vitality into this then-stagnant field of electronics.


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