Grigori Perelman

Grigori Perelman was born in Leningrad in 1966 and showed exceptional mathematical ability from childhood, winning a gold medal with a perfect score at the International Mathematical Olympiad in 1982. He trained at Leningrad State University and spent time at research institutes in the United States in the early 1990s, impressing colleagues before returning to Russia to work at the Steklov Institute in St Petersburg.

He then turned to the Poincaré conjecture, a problem about the shape of three-dimensional space that had gone unsolved since 1904 and was considered one of the hardest open questions in topology. Working largely in isolation over several years, he built on earlier work by Richard Hamilton on a technique called Ricci flow, and in 2002 and 2003 posted a series of papers online that, after intense scrutiny by other mathematicians, were confirmed to contain a complete proof.

The achievement earned him the Fields Medal in 2006, which he refused to accept, and in 2010 the Clay Mathematics Institute awarded him one million dollars as one of its Millennium Prize problems, which he also turned down, saying he did not believe his contribution was any greater than Hamilton's.

He withdrew from mathematics and largely from public life afterward, living quietly in St Petersburg and declining almost all requests for interviews or appearances.