Klaus Roth

Klaus Friedrich Roth (Roth rhymes with "both") (b. 29 October 1925) is a British mathematician known for work on diophantine approximation, the large sieve, and irregularities of distribution. He was born in Breslau (then in Germany, now Wrocław in Poland) but was raised and educated in the UK. He graduated from Peterhouse, Cambridge in 1945. He was a student of Harold Davenport.

His definitive result, now known usually as the Thue-Siegel-Roth theorem, but also just Roth's theorem, dates from 1955, when he was a lecturer at University College London. He was awarded a Fields Medal in 1958 on the strength of it. In 1956 he established that subsets of the integers of positive density must contain infinitely many arithmetic progressions of length three, thus establishing the first non-trivial case of what is now known as Szemerédi's theorem. He became a professor at University College in 1961, and moved to a chair at Imperial College London in 1966, where he remained until 1988.