Stanley Mandelstam was born in Johannesburg, South Africa, on 12 December 1928 and brought up in the Natal Midlands, the son of a grocer who had recently emigrated from Latvia and a schoolteacher.
After he finished school, the family returned to Johannesburg and he embarked on a degree in chemical engineering at the University of the Witwatersrand.
This was a vocational qualification, as his mother had wished, but Professor Mandelstam’s real passion was mathematical physics. He therefore went on to a BA at the University of Cambridge (1954), followed by a PhD at the University of Birmingham (1956).
He continued his research at Birmingham for a further year and then moved to the US as a Boese fellow at Columbia University in New York (1957-58). He moved to the University of California, Berkeley as an assistant research physicist (1958-60) and was then appointed professor of mathematical physics at Birmingham (1960-63).
After that spell, however, Professor Mandelstam brought to an end his crossings of the Atlantic and settled for good at Berkeley as professor of theoretical physics. He was to remain there until he retired and became emeritus in 1994, although with short breaks as a professeur associé at Paris-Sud University.
A leading authority on particle theory, and particularly string theory, he had in 1958 already developed a system of coding known as Mandelstam variables to represent the energy, momentum and scattering angles of particles.
In 1991 he was awarded the prestigious Dirac Medal for Theoretical Physics by the International Centre for Theoretical Physics in Trieste, Italy, yet was also notably modest about his achievements, regularly taught undergraduates and, unlike everybody else, never referred to his coding system as Mandelstam variables. On his website, he simply said: “My research concerns string theory…Although much has been learned, some basic questions remain, and I hope to be able at least to understand the simpler of these questions.”
“Stanley Mandelstam was simply a giant in theoretical physics. He made a tremendous amount of fundamental contributions to the development of quantum field theory and string theory,” said Yasunori Nomura, current director of the Berkeley Center for Theoretical Physics.
“He made crucial contributions throughout virtually all aspects of quantum field theory and string theory, including the early bootstrap program, the Regge theory and supersymmetric field theories. But it took some time for me to realise this (even after I joined the Berkeley theory group as a postdoc), because he never banged his own drum.”
Professor Mandelstam died on 23 June.