**John Lewis** was a Welsh applied mathematican who worked on quantum mechanics.

- Although born in Swansea, John was brought up in Cardiff where he attended Marlborough Road Elementary School for Boys.
- After studying at the elementary school, John attended Cardiff High School from 1942 to 1948.
- It was at this school that John received excellent teaching in mathematics from Arthur Davies.
- By a strange coincidence, many years later Lewis wrote a paper with Brian Davies An operational approach to quantum probability (1970).
- While at Queen's University, Lewis met Maureen MacEntee, who was an organic chemist.
- Lewis was a keen rower and during his time at Queen's University he was captain of the boat club, and a very successful captain too for they won the national senior championship for eights in 1953.
- When Lewis began undertaking research at Queen's University, Belfast, in 1952 his official Ph.D. advisor was Bates but he was greatly assisted by Dalgarno.
- Lewis was awarded his doctorate in 1955 for his thesis Quantal Calculations Relating to Certain Rate Processes.
- It has come to be known as the Dalgarno-Lewis sum rule or method.
- Lewis's first publication Inelastic heavy particle collisions involving the crossing of potential energy curves, written jointly with David Bates, appeared in 1955 and in the same year his first joint publication with Alex Dalgarno was published, namely The exact calculation of long-range forces between atoms by perturbation theory.
- Two further papers by Lewis appeared in 1955, the single authored paper Ionic configuration interaction in some excited states of the hydrogen molecule and the paper Properties of the hydrogen molecular ion written jointly with Martin R C McDowell, and Benno L Moiseiwitsch.
- After the award of his doctorate, Lewis went to the University of Oxford where he was a postdoctoral student working with Charles Coulson, the Rouse Ball Professor of Mathematics.
- Lewis and Coulson, together with A D Buckingham, published The quadrupole moment of a hydrogen atom in a uniform field (1956).
- After a year as a postdoctoral student, Lewis spent sixteen further years at Oxford.
- Towards the end of his time in Oxford, Lewis took sabbatical leave, spending 1969 at the Institute for Advanced Study in Princeton and 1970 as a Visiting Scientist at Rockefeller University In New York.
- We note that Rockefeller University was only given this name five years before Lewis was a visitor there; before that it was part of the State University of New York.
- The invitation to Rockefeller University came from Mark Kac who Lewis had met in Oxford in the spring of 1969.
- During the years from 1956 to 1972 Lewis's interests broadened considerably.
- Lewis then wrote two papers with Christopher Martin Edwards, who was a fellow in mathematics at the Queen's College, Oxford, on Twisted group algebras.
- Martin Edwards had been one of Lewis's doctoral students, obtaining his doctorate from Oxford in 1966.
- Lewis also wrote a paper with David Joseph Judge on the commutation relation in quantum mechanics.
- While at Rockefeller University Lewis had worked with Mark Kac who interested him in quantum probability, dissipation in quantum mechanics and Bose-Einstein condensation.
- Their collaboration led to Kac spending further time at Oxford later in 1970 after Lewis's visit to the United States.
- At Rockefeller University, Lewis had also collaborated with George William Ford (known as Bill), to whom he had been introduced by Kac.
- Lewis also met Bob O'Connell from Louisiana State University and Ford and O'Connell became long term collaborators with whom Lewis wrote many papers.
- We have counted 13 Ford-Lewis-O'Connell three-author papers, and 5 further papers of Lewis with Ford, some with additional authors.
- In 1972 Lewis left Oxford and returned to Ireland where he was appointed to a Senior Professorship in the School of Theoretical Physics of the Dublin Institute for Advanced Studies.
- The position had become vacant due to the retirement of John Lighton Synge who had built the School into a major international one.
- At the time of Lewis's appointment, Lochlainn O'Raifeartaigh was the Director of the School of Theoretical Physics.
- In January 1975 Lewis was appointed as Director of the School when O'Raifeartaigh made an extended visit to the Institut des Hautes Études Scientifiques at Bures-sur-Yyvette near Paris.
- In 1977, he published the monograph Dilations of Irreversible Evolutions in Algebraic Quantum Theory which he had written in a collaboration with David E Evans who had come from Oxford to join Lewis at the Dublin Institute for Advanced Studies in 1975.
- In March 1988 a deputation from the Institute, including Lewis, met with the Department of Education.
- Lewis and the other School directors made presentations to the Secretary of State making a strong case to continue funding the Institute.
- Lewis was keen to collaborate with other mathematicians as can be clearly seen from his publication list.
- In 1989 the Steklov Mathematics Institute invited Lewis to visit Moscow and Kiev as a Guest of the USSR Academy of Sciences.
- After a revolutionary insight on how to measure Internet traffic, John persuaded visionaries from the Computer Laboratory in Cambridge and the Swedish operator Telia to join him in a three-year research contract funded by the European Commission.
- Although the Moscow visit had given him ideas, there was a practical reason why Lewis moved his research in this direction.
- Lewis always declared that he was self-taught in pure mathematics.
- Lewis received notable honours for his contributions.
- Lewis retired from his position at the Dublin Institute for Advanced Studies in 2001.
- John's impressive scientific work is a monument to our memory of him.
- Many mathematicians would not have considered academic life without John's influence.
- While considering John's contribution to science, we should not forget the contributions that he made to many of our lives.
- An old friend of John's from his time at Oxford put it well when he said: "John was a lovely man and a perfect fit to my ideal of an academic: a man of great learning, lightly worn, and no conceit of himself."

Born 15 April 1932, Swansea, Wales. Died 21 January 2004, Dublin, Ireland.

View full biography at MacTutor

Origin Wales

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive