Imre Z. Ruzsa

Imre Z. Ruzsa (born 23 July 1953) is a Hungarian mathematician specializing in number theory.

Life He graduated from the Eötvös Loránd University in 1976. Since then he has been at the Alfréd Rényi Institute of Mathematics of the Hungarian Academy of Sciences. He was awarded the Rollo Davidson Prize in 1988. He was elected corresponding member (1998) and member (2004) of the Hungarian Academy of Sciences. He was invited speaker at the European Congress of Mathematics at Stockholm, 2004, and in the Combinatorics section of the International Congress of Mathematicians in Madrid, 2006. In 2012 he became a fellow of the American Mathematical Society.

Work With Endre Szemerédi he proved subquadratic upper and lower bounds for the Ruzsa–Szemerédi problem on the number of triples of points in which the union of any three triples contains at least seven points. He proved that an essential component has at least (log x)1+ε elements up to x, for some ε > 0. On the other hand, for every ε > 0 there is an essential component that has at most (log x)1+ε elements up to x, for every x. He gave a new proof to Freiman's theorem. Ruzsa also showed the existence of a Sidon sequence which has at least x0.41 elements up to x.

Selected publications