Stanley Mandelstam

Born on 12 December 1928 in Johannesburg, South Africa, Stanley Mandelstam was a leading 20th-century mathematical and particle physicist. He earned a degree from the University of the Witwatersrand in chemical engineering, but his true passion was mathematical physics. He earned a PhD in the subject from the University of Birmingham, UK, in 1956. Two years later he introduced what are now called Mandelstam variables, which represent the energy, momentum, and angles for pairs of particles that scatter off each other. Throughout his career Mandelstam contributed crucial mathematical insights to quantum field theory, supersymmetry, and string theory. He won the Dirac Medal for Theoretical Physics in 1991. Mandelstam routinely taught undergraduates at the University of California, Berkeley, and he was described as so modest that many people who knew him were unaware of his achievements. He died in June 2016. (Photo credit: AIP Emilio Segrè Visual Archives)

Date in History: 12 December 1928