Sin-Itiro Tomonaga
1906–1979, Tokyo, Japan, Tokyo, Japan
Japanese theoretical physicist who formulated a covariant quantum electrodynamics and its renormalization, sharing the 1965 Nobel Prize with Feynman and Schwinger.
Tomonaga worked in Yoshio Nishina's group at RIKEN and studied with Heisenberg in Leipzig before the war. Working in wartime isolation, he published in 1943 a manifestly relativistic formulation of quantum field theory — the 'super-many-time' theory — and in 1946–48 his group developed the renormalization program that removed the divergences of QED, independently of Schwinger and Feynman.
Nobel-winning work
Tomonaga's 1965 Nobel Prize recognized his fundamental work in quantum electrodynamics. His 1943 theory recast quantum field dynamics in a fully relativistic spacetime picture, and after the war his Tokyo group applied it to the newly measured Lamb shift.
By systematically identifying infinite self-energy and vacuum-polarization terms and absorbing them into redefined masses and charges — the renormalization procedure — they obtained finite, extremely accurate predictions such as the electron's anomalous magnetic moment, establishing QED as the most precisely tested theory in physics.
Workplaces: Tokyo University of Education (Tsukuba), Institute of Physical and Chemical Research (RIKEN)
Japan