Stefan Vajda was one of the leading figures in the field of mathematics known as Operational Research which emerged just after the Second World War. Operational Research grew from wartime attempts to solve problems of minimising costs of production, supply and transportation. It was a period of transition in a long career during which Vajda never lost his enthusiasm for mathematical ideas or failed to encourage others to explore them.
When the war ended, he was pleased to be one of the first new British citizens, just before taking over as Head of the Mathematics group at the Admiralty. He enjoyed contacts at this time with statisticians in Cambridge including David Cox and Henry Daniels, later a colleague at Birmingham University. Another young mathematician, Martin Beale, agreed to join the Admiralty, but only when he had first completed a book on bridge.
An optimisation technique called Linear Programming was then developing in the United States. This had wide applications in industry and both Vajda and Beale became interested. They developed it further in Britain and, later, it became the subject of Vajda's first book, Linear Programming, published in 1956, which was translated into many languages. Since the technique was central to the growth of Operational Research as a separate discipline, the book established his international reputation. He enjoyed writing about the mathematical problems, and in all produced 15 books on subjects ranging from manpower planning to mathematical games.
Stefan Vajda (Steven to his younger friends) was born in Budapest in 1901 and moved with his family to Vienna in 1903, where he was educated. He first entered university as an engineering student, but switched to actuarial training. When he qualified, but could not find work, he turned to mathematics for a PhD. Later, he attended lectures by David Hilbert and other leading mathematicians in Gottingen, including Emmy Noether who provided a contact in insurance. This led to Vajda's first job as a consultant in Romania and then to what must have seemed a more secure position as an actuary in Vienna, where he was married in 1929.
It is difficult to imagine the anxiety and hazards of escape from Austria in 1939: Vajda's two children were sent first to Sweden and his wife Eva was admitted to the United Kingdom as a domestic servant. Vajda only obtained a visa because his friend Karl Popper, the philosopher, had offered him a job in New Zealand. In fact, he never went there because war was declared and the family were reunited in England.
At the outbreak of war, the family had a short period of internment on the Isle of Man with many other refugees from Europe. Internment on the Isle of Man was not an unpleasant experience. Vajda spent some of his time there teaching mathematics; one of his pupils was Claus Moser. In effect, a college was formed, and several students passed entrance examinations for London University. After a few months, however, most of them were released. Vajda found work with an insurance company in Epsom.
Before the war ended he was involved in mathematical research for the Admiralty - which led to Operational Research. His association with the Admiralty had begun early in 1944 after an actuary, Hilary Seal, invited him to join a new Statistics section there. Vajda's reaction was to ask how an "enemy alien" could possibly work for the Ministry of Defence.
He worked for the Admiralty until 1965 when, aged 63, he became the first Professor of Operational Research at Birmingham University. He set up a group in the Engineering Production Department and I first met him when I was invited to give a seminar. He continued research there after formal retirement until 1973, when he was invited to move to Sussex University by Pat Rivett. Since then, he had worked enthusiastically as a teacher and supervisor of research projects in both Operational Research and Statistics groups. His penetrating questions were a regular feature of our seminars.
Stefan Vajda, actuary and mathematician: born Budapest 20 August 1901; Head of Mathematics, Birmingham University 1952-65, Professor of Operational Research 1965-68, Senior Research Fellow 1968-73; Visiting Professor, Sussex University 1973-95; married 1929 (one son, one daughter); died Brighton 10 December 1995.
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