By analogy, Nambu noted that when a group gathers in a large, open area, people usually look in a variety of directions. But sometimes, when one person begins looking in one direction, those in the crowd do likewise. “That’s a broken symmetry,” Nambu said, a behavior that subatomic particles also display.
In 1965 Nambu, in collaboration with Moo-Young Han, now of Duke University, developed the forerunner of the modern theory of quantum chromodynamics, which accounts for the nuclear forces that bind protons and neutrons into atomic nuclei. Shortly thereafter Nambu and two others, acting independently, showed that physicists needed to abandon their concept of point-like elementary particles and replace it by a dynamics of strings acting in accordance with relativity theory.
“Once again, Nambu’s deep insight led to a vast scientific enterprise—one which continues even today, nearly half a century after his original papers,” Harvey said.
‘I liked it so much, I ended up staying’
Nambu was born Jan. 18, 1921 in Tokyo. His interest in science developed in high school after his father showed him some science magazines. In college, one of his professors was Hideki Yukawa, a leading particle physicist of his day. He received his bachelor’s degree in 1942 from the University of Tokyo. He was then drafted into the Japanese army and was assigned to follow the radar work of Sin-ichiro Tomonaga, the leading theoretical physicist for one of the competing military services.
Nambu married Chieko Hida in 1945. He became an associate professor at the newly created Osaka City University at the age of 29 in 1950. He completed his doctorate in 1952 from the University of Tokyo.
Nambu retained his appointment at Osaka City University until 1956, but went to the Institute for Advanced Study in Princeton, N.J., in 1952 upon the recommendation of Tomonaga to study with J. Robert Oppenheimer. Freund told the Chicago Tribune in 2008 that while at the Institute for Advanced Study, Nambu summoned the courage to introduce himself to Albert Einstein, whom Oppenheimer had tried to insulate from visits by junior researchers.
“Einstein was just happy that finally someone had come to talk with him,” Freund said.
Nambu joined the University of Chicago as a research associate in 1954, becoming associate professor in 1956 and professor in 1958. He obtained U.S. citizenship in 1970. He had not intended to spend his entire career at UChicago, “but I liked it so much, I ended up staying,” Nambu said in 2008. He found that even in the rarefied intellectual atmosphere of the University’s physics department, “everybody treated everybody else as members of a big family.”
Nambu served as chairman of the physics department from 1974 to 1977. He was named the Harry Pratt Judson Distinguished Service Professor in 1977, and retired as professor emeritus in 1991.