János Kollár (born 7 June 1956) is a Hungarian mathematician, specializing in algebraic geometry.
Kollár began his studies at the Eötvös University in Budapest and later received his PhD at Brandeis University in 1984 under the direction of Teruhisa Matsusaka with a thesis on canonical threefolds.
[1] Kollár is known for his contributions to the minimal model program for threefolds and hence the compactification of moduli of algebraic surfaces, for pioneering the notion of rational connectedness (i.e. extending the theory of rationally connected varieties for varieties over the complex field to varieties over local fields), and finding counterexamples to a conjecture of John Nash.
(In 1952 Nash conjectured a converse to a famous theorem he proved,[2] and Kollár was able to provide many 3-dimensional counterexamples from an important new structure theory for a class of 3-dimensional algebraic varieties.)
[3] Kollár also gave the first algebraic proof of effective Nullstellensatz: let
[4] Kollár is a member of the National Academy of Sciences since 2005 and received the Cole Prize in 2006.
[9] In 1990 he was an invited speaker at the International Congress of Mathematicians (ICM) in Kyōto.
In 1996 he gave one of the plenary addresses at the European Mathematical Congress in Budapest (Low degree polynomial equations: arithmetic, geometry and topology).
He was also selected as a plenary speaker at the ICM held in 2014 in Seoul.
As a high school student, Kollár represented Hungary and won Gold medals at both the 1973 and 1974 International Mathematical Olympiads.