**Raphael Robinson** was an American mathematician who was interested in a wide variety of problems including number theory and tilings.

- Robinson entered the University of California at Berkeley from where he graduated with a B.A. in 1932 and an M.A. in the following year.
- The Great Depression began in 1929 while Robinson was an undergraduate and by 1932, when he graduated with a B.A., one quarter of the workers in the United States were unemployed.
- The Depression lasted for around ten years so when Robinson began to look for a post in 1935 there was still a great scarcity of college positions and those which did exist paid very low wages.
- By 1937 employment opportunities were improving and Robinson was offered a full-time instructorship at Berkeley which he gladly accepted.
- In 1939 Robinson taught a course in number theory and one of his students was Julia Bowman.
- Raphael and Julia began going for walks together; on these he would teach her more mathematics which she found very exciting.
- When Bowman's job applications failed, Neyman found a small amount of money to allow her to stay on at Berkeley as his assistant and in 1941 she was awarded her M.A. By this time Raphael and Julia planned to marry so Julia turned down a civil service job to remain at Berkeley as a teaching assistant.
- Robinson was steadily promoted, becoming a full professor in 1949.
- Even in retirement Robinson owned no casual clothes.
- Julia Robinson died in July 1985 and, in the following year, Raphael established the Julia Bowman Robinson Fund for fellowships for graduate students in mathematics at Berkeley.
- On 4 December 1994 Robinson suffered a stroke from which he never recovered, dying eight weeks later.
- Robinson worked on a wide variety of mathematical topics.
- Robinson obtains best possible results using methods involving continued fractions, their convergents and their secondary convergents.
- In a series of papers Robinson showed that a number of mathematical theories are undecidable.
- In 1953 Tarski, together with Robinson and Mostowski, published Undecidable theories.
- As we mentioned above, Robinson worked in number theory and he used the earliest computers to obtain results.
- At the time that Robinson wrote this paper the last five of these primes were larger than any that had previously been found.
- it is refreshing and stimulating to encounter one of Robinson's papers.
- In a major paper Undecidability and nonperiodicity for tilings of the plane published in 1971, Robinson continued to study problems of a kind that he had examined for a long while.
- Robinson had already made a substantial contribution to problems of this type in earlier papers.
- In the 1971 paper mentioned above, Robinson asks a question about undecidability and nonperiodicity results for tilings of the hyperbolic plane.
- Undecidability involves the halting problem for Turing machines and in 1991, when Robinson was aged 80, he published Minsky's small universal Turing machine which describes a universal Turing machine with 4 symbols and 7 states.

Born 2 November 1911, National City, California, USA. Died 27 January 1995, Berkeley, California, USA.

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Origin Usa

**Oâ€™Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive