Lars Ahlfors

Lars Valerian Ahlfors was born in Helsinki and studied mathematics at the University of Helsinki, where he came under the influence of Ernst Lindelöf and Rolf Nevanlinna, the founders of the Finnish school of function theory. In 1929 he used a new length–area argument to prove Denjoy's conjecture: an entire function of finite order $p$ has at most $2p$ distinct asymptotic values. The following year he solved a problem of André Bloch, a result now called Bloch's theorem, and in 1935 he published his landmark theory of covering surfaces.

Ahlfors taught at the University of Helsinki and, after spending the war years partly in Finland and at the University of Zürich, moved to Harvard University in 1946, where he remained for the rest of his career. His work with quasiconformal mappings transformed the study of Riemann surfaces: together with Lipman Bers he developed the theory of Teichmüller spaces, and he proved finiteness theorems for Kleinian groups, including the finiteness theorem for finitely generated Kleinian groups whose limit set has zero area. His monograph on complex analysis became a standard textbook.

At the first Fields Medal award ceremony, in Oslo in 1936, Ahlfors shared the inaugural medal with Jesse Douglas; he was unable to attend and the medal was accepted on his behalf. He received the Wolf Prize in Mathematics in 1981 for his seminal discoveries and the creation of powerful new methods in geometric function theory. He died in Pittsfield, Massachusetts, in 1996.

Workplaces: University of Helsinki, Harvard University

Finland, United States

Contributions, linked to the library