Tomonaga, Sin-Itiro

[tomonahga] (1906–79) Japanese theoretical physicist: a founder of quantum electrodynamics (QED).

Tomonaga graduated in physics at Kyoto University and studied with at Leipzig before becoming professor of physics at Tokyo (1941) and then president of the university (1956).

Like others, Tomonaga started to develop a relativistic theory of the quantum mechanics of an electron interacting with a photon (1941–3). During the Second World War, he, were unaware of each other’s work, and it was not until 1947 that it was realized that all three had arrived independently at solutions to the problem of linking special relativity with quantum physics, solutions which were shown to be identical by . Tomonaga realized the value of a theory that could describe high-energy subatomic particles and he was responsible for the idea that two particles interact by exchanging a third virtual particle between them. The interaction is then like the momentum exchange when one rugby player passes the ball to another. The resulting theory is called quantum electrodynamics (QED) and for its discovery Feynman, Schwinger and Tomonaga shared the 1965 Nobel Prize for physics.