by David G. Kendall
© Oxford University Press 2004 All rights reserved
Reuter, (Gerd Edzard) Harry (1921-1992), mathematician, was born in Berlin on 21 November 1921, the son of Dr Ernst Rudolf Johannes Reuter (1889-1953), politician, and his wife, (Gertrud) Charlotte, née Scholz (1901-1977). His father, a leading Social Democrat, was twice imprisoned for anti-Nazi activities before escaping, in 1935, to Turkey, where he was professor of municipal theory and practice at the University of Ankara for the duration of the war. After the war he returned to Germany and became burgomaster of what was then left of Berlin. He held office during the Soviet blockade of 1948-9, embodying personally that city's dogged resistance. His memory was enshrined in the Ernst Reuter Platz in Berlin, and in the Free University which he helped to found in 1948.
In 1935 Harry Reuter, like many others, was sent from Germany to England, where he joined the family of (John) Charles and Greta Burkill in Cambridge. They were both for many years notable figures in the university, Charles as a distinguished mathematician and later master of Peterhouse, and Greta later as a principal founder of the Cambridge University Centre. The Burkills also had another adopted mathematical son, Harry Burkill, who said that 'in that household mathematics was in the air' (private information). Reuter was educated at the Leys School in Cambridge from 1935 to 1938, where he was supported by a generous arrangement set up by the school and the Society of Friends' Germany emergency committee. There he distinguished himself on the hockey field. From the Leys he went on to Trinity College, Cambridge, taking part two of the mathematical tripos in 1941. In the latter year he joined the Royal Naval Scientific Service, and spent the war mostly in London. On one occasion he was sent on naval business to the north of Scotland, and was required to show both his Admiralty pass and his British passport. The entry 'Place of birth: Berlin' caused some consternation. On 9 August 1945 Reuter married Eileen Grace Legard (b. 1921), a teacher; they had one son and three daughters.
When the war ended Reuter was sent to Germany to debrief the scientists in various German institutions. There he learned of a mathematical research institute at Oberwolfach in the Black Forest, and reached it just in time to prevent it from being converted into an officers' club. From then on Oberwolfach became the principal European research centre for mathematics. He returned briefly to Cambridge as a research pupil of Frank Smithies, who introduced him to functional analysis. Then, in 1946, he moved to Manchester, where he joined the formidable mathematics department presided over by Maxwell Herman Alexander (Max) Newman. In the late 1940s he worked closely with Dame Mary Lucy Cartwright and John Edensor Littlewood on non-linear differential equations, and with Ernst Sondheimer on the theory of the anomalous skin effect in metals. The latter laid the foundations for subsequent work by Sir Brian Pippard and others on electronic behaviour in metals. In the early 1950s Reuter wrote, with Walter Ledermann, two papers on Markov processes. These were followed by a more extensive collaboration between Reuter and David Kendall on Markov semigroups. This work arose from the recent discovery by the Soviet mathematician A. N. Kolmogorov of two remarkable 'pathological' Markov processes, known as K1 and K2. Reuter and Kendall presented the results of their investigation of these processes in a joint paper at a mathematical congress in Amsterdam at which Kolmogorov was present, and then went on to investigate the associated ergodic theorems and to solve the problem of determining the limits pij(∞) directly from a knowledge of the infinitesimal generator.
Reuter spent a brief period at Yale in 1958-9 (where he was able to work with the distinguished American mathematician Will Feller) before moving to Durham to take up the chair in pure mathematics. In 1965 he moved to Imperial College, London, where he remained until his retirement in 1983 as professor of mathematics and head of the mathematics department. He was closely involved, with Kendall and others, in setting up the stochastic analysis group to promote probabilistic activity within both the London Mathematical Society and the Royal Statistical Society. He was a vice-president of the London Mathematical Society and its representative on the Applied Probability Trust, and first chairman of the Rollo Davidson Trust. His work on Markov processes brought him international recognition, especially in China, where 'respect for his achievements stopped little short of reverence' (The Times, 9 May 1992). His work in applied fields--including studies of the dynamics of fluid flow, and (with Colin Atkinson and C. J. Ridler-Rowe) studies of the dynamics of epidemics--was also widely appreciated.
Harry Reuter was a great pure mathematician, a great applied mathematician, and an exceptional probabilist. He was also a gifted teacher, leaving behind fifteen distinguished research pupils. His later days were very peaceful, despite a progressive illness which he bore with patience and dignity. After his retirement he and his wife, Eileen, moved to Cambridge, where friends and colleges would always be sure of a warm welcome, and equally sure to find support and wisdom, and a very gentle reproof if they had done something really outrageous. Indeed, for many Reuter was a touchstone of integrity. Many specious compromises were quietly dropped after a chat with him. He died in Cambridge of ischaemic heart disease and bronchopneumonia on 20 April 1992. He was survived by his wife and four children, whose love and support had greatly enriched his life. He was buried at Cambridge.
DAVID G. KENDALL
Sources
private information (2004) [Mrs Eileen Reuter]
personal knowledge (2004)
WWW, 1991-5
Bulletin of the London Mathematical Society, 27 (1995), 177-88
The Times (9 May 1992)
The Times (18 May 1992)
Daily Telegraph (25 June 1992)
Likenesses
photograph, repro. in Bulletin of the London Mathematical Society
Wealth at death
under £125,000: probate, 9 June 1992, CGPLA Eng. & Wales
[http://www.oxforddnb.com/view/article/54643]
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