## Professor David Olive, CBE FRS FLSW

Professor Olive receiving the Dirac Medal from Professor Miguel Virasoro

Professor David Olive, who has died in Cambridge aged 75, was one of the pre-eminent theoretical physicists of his generation. His academic career encompassed the University of Cambridge, CERN, Imperial College and Swansea University, where together with Ian Halliday he founded the theoretical particle physics group in 1992. He made seminal contributions to S-matrix theory, superstrings, gauge theories and mathematical physics and was awarded the Dirac Medal by the International Centre for Theoretical Physics in Trieste in 1997, with his long-standing collaborator Peter Goddard. He was a Fellow of the Royal Society and a Founding Fellow of the Learned Society of Wales.

David was born in Middlesex in 1937 and educated at the Royal High School, Edinburgh and Edinburgh University. He was an outstanding student, his only shortcoming being his notoriously illegible handwriting, reputedly the origin of an early Who's Who entry listing his interests as “music and gold”. (David was a keen golfer.) He then moved to St John's College, Cambridge, obtaining his PhD under the supervision of John Taylor in 1963. After a short postdoctoral appointment at the Carnegie Institute in Pittsburgh, David returned to Cambridge as a Fellow of Churchill College, becoming a Lecturer in the Department of Applied Mathematics and Theoretical Physics (DAMTP) in 1965. Here he made key contributions to the approach to particle physics known as S-matrix theory. His 1966 book “The Analytic S-matrix'”, co-authored with Richard Eden, Peter Landshoff and John Polkinghorne, remains the definitive text on the subject, known affectionately by generations of students simply as “ELOP'”.

In 1971, David made what he has described as a “momentous personal decision” to sacrifice his tenured position in Cambridge and move to the Theory Division, CERN as a fixed-term staff member. He was motivated by the desire to devote himself to working in the stimulating group of physicists being assembled by Daniele Amati on the subject he had come to regard as the theory of the future, originally known as the dual resonance model but shortly to be recognised as string theory. In CERN, David began the collaborations with the circle of string theorists who would shape his outlook and career, many of whom feature in his memoir “From Dual Fermion to Superstring”, published in “The Birth of String Theory”, eds. Cappelli *et al*., CUP. His work at CERN, in part in collaboration with Lars Brink and Ed Corrigan, initially focused on the consistent formulation of dual fermion amplitudes, generalising the existing bosonic models. This period saw several of David's major contributions to string theory, including the “Gliozzi-Scherk-Olive (GSO) projection” which elucidated the role of spacetime supersymmetry in ensuring consistency of the dual fermion model and was to prove an essential step in establishing 10-dimensional superstring theory. He was one of the first to become convinced of the conceptual revolution whereby string theory is viewed as a unified theory of all particle interactions, including gravity, rather than simply as a model of hadrons. This vision informed his highly influential plenary talk at the 1974 “Rochester” conference in London.

In 1977, David returned to the U.K. to take up a lectureship at Imperial College, becoming Professor in 1984 and Head of the Theoretical Physics Group in 1988. He had by now established a highly productive collaboration with Peter Goddard and together they produced a series of seminal papers on the mathematical foundations of string theory, notably on Virasoro and Kac-Moody algebras and their representations and relation to vertex operators. One prescient outcome of their work on algebras and lattices was the identification of the special role played by the two Lie groups SO(32) and E8 x E8, which would shortly be shown by Michael Green and John Schwarz to exhibit the famous anomaly cancellation that led to the renaissance of string theory in 1984.

This body of work from 1973-83 was recognised with the award of the prestigious Dirac Medal in 1997 to Goddard and Olive “in recognition of their far-sighted and highly influential contributions to theoretical physics. They have contributed many crucial insights that shaped our emerging understanding of string theory and have also had a far-reaching impact on our understanding of 4-dimensional field theory.”

The Dirac Medal also recognised a second major line of research pioneered by David, on duality symmetries in gauge field theories. Remarkably, this work was also to play a key role in later developments of string/M theory. While still at CERN, David had begun to study the magnetic monopoles which 't Hooft and Polyakov had shown existed in non-abelian gauge theories, publishing an influential paper with Peter Goddard and Jean Nuyts. In 1977, together with Claus Montonen, he made the remarkable conjecture that there should exist an electromagnetic dual theory in which the roles of monopoles and gauge bosons are interchanged. In subsequent work with Ed Witten, David showed that this duality is indeed realised in a certain class of supersymmetric theories. This Olive-Montonen duality was later found to emerge from a deeper web of dualities underlying string/M theory, ushering in the second superstring revolution of the mid 1990s.

In 1992, David left Imperial to take up a research professorship in mathematics and physics at Swansea University, where together with Ian Halliday he built the theoretical particle physics group, now one of the leading theory groups in the U.K. He continued to work on mathematical physics, exploring the deep symmetries underlying quantum field theories, especially affine Toda theory. The mathematics of symmetry was a lifelong enthusiasm, suiting David's predilection for clarity, precision and depth which characterised all his work in theoretical physics. He was a generous supervisor and teacher, guiding many PhD students who have gone on to accomplished careers around the world. His wide circle of friends, colleagues and collaborators remember him with respect and affection as a brilliant but unassuming theorist whose insights have become part of the fabric of modern theoretical physics. His retirement was marked by a conference “Strings, Gauge Fields and Duality” held in his honour in Swansea in 2004, which was attended by many of his collaborators together with a new generation of young string theorists whose research has built on the foundations established in David's pioneering work.

David was a devoted family man. He married Jenny in 1963 while at Cambridge and they have daughters Katie and Rosalind. Jenny, a mathematician in her own right, provided specialised maths support to undergraduate physics students in Swansea and wrote the popular textbook “Maths - a student survival guide” (CUP). As well as his continuing battles with the game of golf, which reflected his Scottish upbringing, David's time at CERN led to enthusiasms for hiking and skiing. He had a lifelong love of music, over the years building an exceptional collection of classical music recordings. He had a keen sense of the history and culture of mathematics and theoretical physics and in his later years was researching a history of physics in Swansea.

David travelled widely throughout his career, including substantial visits to the Mittag-Leffler Institute in Stockholm, the Newton Institute in Cambridge, NORDITA and the Niels Bohr Institute in Copenhagen, Chalmers University in Gothenburg, the University of Utrecht as Kramers Professor, IFT Sao Paulo, the University of California at Berkeley as Miller Professor, and the Institute for Advanced Study, Princeton. He received many honours in addition to the Dirac Medal. He was elected a Fellow of the Royal Society in 1987. In 2007, he became a Foreign Member of the Royal Society of Arts and Sciences in Gothenburg and in 2010 was a Founding Fellow of the Learned Society of Wales. In 2002, David received a CBE in the Queen's New Year's Honours List in recognition of his services to theoretical physics.