He introduced the relativistically invariant Mandelstam variables into particle physics in 1958 as a convenient coordinate system for formulating his double dispersion relations .
Stanley Mandelstam ( 12 December 1928 -- 23 June 2016 ) was a South Africa - born American theoretical physicist of Jewish ancestry .
Stanley Mandelstam introduced the relativistically invariant physicist variables into particle physics in 1958 as a convenient coordinate system for formulating Stanley Mandelstam 's double dispersion relations .
Stanley Mandelstam ( 12 December 1928 -- 23 June 2016 ) was a South Africa - born American theoretical physicist of Jewish ancestry .