Lochlainn O'Raifeartaigh, class '50

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Lochlainn O'Raifeartaigh, who died on November 18, aged 67, was a distinguished physicist of international repute. He was one of the world-leaders in the theory of elementary particles. Like the institution he served, he was far better known outside Ireland than within. From 1960 to the time of his death, he was a Professor at the School of Theoretical Physics in the Dublin Institute for Advanced Studies (DIAS).

Lochlainn O'Raifeartaigh was born in Dublin on 11 March 1933 to Tarlach and Neans O'Raifeartaigh. Tarlach was an Irish scholar and civil servant, who, as Secretary of the Department of Education and later as first Chairman of the Higher Education Authority, was instrumental in the development of university education in Ireland. In 1958, Lochlainn married Treasa Donnelly, a Celtic Studies graduate of The Queen's University, Belfast, who came from County Tyrone like his father. They had met in the Donegal Gaeltacht and shared a life-long interest in the Irish language and culture. Treasa was the perfect partner for him; her instinctive understanding of his brilliance moderated by her own down-to-earth common sense supported his work while raising five children as they moved around the world. Their travels enabled them to expand their shared love of other languages and cultures.

Lochlainn attended Castleknock College and University College, Dublin, graduating with first class honours in Mathematical Physics. He entered DIAS in 1956. While a student, he had attended lectures by the Nobel Laureate Erwin Schrodinger, the first Director of the School of Theoretical Physics. Schrodinger returned to Vienna in 1956 and Lochlainn worked with John L. Synge on the Theory of Relativity. In 1957, he was awarded a Studentship by the Council of DIAS to study under Waltet Heitler, one of the pioneers of Quantum Field Theory, at the University of Zurich where he was awarded his Doctorate in 1960. He returned to DIAS in 1961 as Assistant Professor and was elected to Membership of the Royal Irish Academy at the age of 29. Later he was elected to membership of the Academia Europaea.

Those who have struggled with the elements of group theory for Leaving Certificate Mathematics may be surprised to learn that the subject has profound implications in physics. Lochlainn O'Raifeartaigh specialised in the application of group theory to physics. His research on the symmetries of physical theories attracted much attention particularly in the United States. He spent the winter of 1963-4 at the Madras Institute for Mathematical Sciences and in the autumn of 1964 he went on extended leave from DIAS to Syracuse University in New York State. While at Syracuse he made an important discovery, known now as the O'Raifeartaigh Theorem. In it he showed the impossibility of combining relativistic symmetry with other symmetries in a non-trivial way. Its announcement made him famous overnight. It also brought to an abrupt end the research programmes of many of his colleagues.

His future career in the United States was now assured. He chose instead to return to DIAS 1968 as a Senior Professor, after spending one year at The Institute for Advanced Study at Princeton.

Under the 1940 Act establishing DIAS, the primary functions of the School of Theoretical Physics are 'the investigation of the mathematical principles of natural philosophy' and 'the training of advanced students in methods of original research'. Lochlainn O'Raifeartaigh attracted a succession of postdoctoral students from around the world, many of whom now occupy chairs of theoretical physics in their own countries. His style epitomised the principle on which the School was founded. The excitement of discovery, driving discussion at the blackboard late into the evening is the best training in methods of original research that one could imagine. The School, De Valera's creation, flourished thanks to Lochlainn's talent for discovery, his infectious enthusiasm and his ability as a teacher.

In introducing the Act to Dail Eireann, De Valera expressed the belief that the founding of the School of Theoretical Physics would enable Ireland to achieve a reputation in theoretical physics comparable to that which it had in the time of William Rowan Hamilton. In recent years, the School has attracted many distinguished Visiting Professors, largely due to Loichlainn O'Raifeartaigh's reputation as a researcher.

As new concepts arose in theoretical particle physics, Lochlainn made a significant contribution to each. In the early 70s, supersymmetric theories arose, bypassing the difficulties described by the O'Raifeartaigh Theorem. A major advance was an idea of his which became known as the O'Raifeartaigh mechanism for the spontaneous breaking of super-symmetry-. The content of his 1975 paper is to be found in almost every text book on super-symmetry. In the early 80's he made a fundamental contribution to the theory of monopoles in gauge theories. His work on gauge theories was consolidated in his book "Group Structure of Gauge Theories" (Cambridge University Press, 1991). Recently he had been applying the expertise gained from his work on two-dimensional conformal field theories to String Theories.

In recent years he received much international recognition, including the von Humbolt Research Award in 1998 and the prestigious Wigner Medal in August 2000, the latter for his 'pioneering contributions to particle physics'. However, he will be remembered by his colleagues as much tor his humility, patience, kindness and humour as for his academic excellence.

Lochlainn O'Raifeartaigh's interests were not confined to physics. He was fluent in Irish, French and German. He was an enthusiastic theatre-goer and keen hill-walker. He put his interest in international politics to good use in the cause of nuclear disarmament; along with the Nobel Laureate Ernest Walton, he helped Michael Fry found the Irish Pugwash group, bringing together physicists and experts on international affairs. His book "The Dawning of Gauge Theory" (Princeton University Press, 1997) showed him to be an accomplished historian of physics.

To his wife Treasa, his sons, Conor, Finbar and Cormac, his daughters Una and Aoife, brothers and fellow Knock men, Conan, class '54 and Tarlach, class '65, and to his many friends and colleagues we extend our deepest sympathy.

Requiescat in Pace