Lochlainn O'Raifeartaigh (/ˈlɒxlɪn oʊˈræfərti/;[1] 11 March 1933 – 18 November 2000) was an Irish physicist in the field of theoretical particle physics.
[2] Most of his scientific career was centred on that city, where he obtained his first degrees at University College Dublin (BA in 1953 and MSc in Mathematical Physics in 1956), and spent from 1968 until his death as Senior Professor at the Dublin Institute for Advanced Studies.
This result, which became known as O'Raifeartaigh's no-go theorem, showed that it was impossible to combine internal and relativistic symmetries other than in a trivial fashion, thus ending a widespread quest by the particle physics community to achieve this fusion.
His interests encompassed the spin-statistics theorem, Kac–Moody and W-algebras, and included early contributions to the theory of non-invariance (dynamical) groups, among much else.
His long and productive career in the application of symmetry methods to theoretical physics was acknowledged by the award of the Wigner Medal in August 2000.