The following obituary was published in CERN Courier volume 40, number 8, October 2000.

James Hamilton 1918-2000

Born in Sligo, Ireland, James Hamilton got his MSc at Queen’s University, Belfast, on the eve of the Second World War. He received his PhD from Manchester in 1948 and then became university lecturer in mathematics and fellow of Christ’s College, Cambridge (1950-1960). He was professor of physics at University College, London, from 1960 until 1964, before joining the Nordic Institute for Theoretical Physics (Nordita) in Copenhagen.

As Nordita professor of elementary particle physics, Hamilton shaped the institute’s research in the field during a crucial period and trained a whole generation of young Nordic physicists. During a period before his retirement at the end of 1985, he also served as Nordita director. He spent an active retirement in Cambridge, continuing with his research and frequently visiting the university.

After early work on problems related to the interaction of radiation with atoms, Hamilton turned to high-energy physics and produced the well known treatise The Theory of Elementary Particles (1959 Oxford). His interests centred on S-matrix theory and he had a leading role in the efforts to understand the structure of resonances and scattering amplitudes using unitarity and analyticity. Some of his results are summarized in his book with B. Tromborg, Partial Wave Amplitudes and Resonance Poles (1972 Oxford).

Hamilton’s most important contribution was probably the development of sophisticated techniques for making very precise amplitude analyses of low-energy hadronic interactions, notably of the pion-nucleon interaction. Here, using dispersion relations among other tools, he and his collaborators were able to improve on the art of phase shift analysis, thereby helping to pave the way to a better understanding of reaction mechanisms and crucial concepts such as Finite Energy Sum Rules and Dolen-Horn-Schmidt duality. His insistence on such sophisticated analysis formed a school that he took with him to Scandinavia and Nordita. He strongly cared for the young Nordic fellows whom he guided.

Hamilton had a life-long interest in mathematical aspects of elementary particle physics and questions relating to causality. He continued to work on these questions during his retirement and published the book Aharonov-Bohm and other Cyclic Phenomena (1997 Springer) just a few years before his death. Hamilton left an important legacy in elementary particle physics. His friendly spirit will be warmly remembered, particularly by his students and colleagues in the Nordic countries and in the UK.

Paul Hoyer, Nordita, and Jens Lyng Petersen, Niels Bohr Institute