Jacob Tsimerman

fl. 1988, Kazan, Soviet Union

Arithmetic and number theoryGeometryFields Medal 2026

Canadian arithmetic geometer at the University of Toronto who turned o-minimality into a core tool of Diophantine geometry; Fields Medalist 2026.

Jacob Tsimerman was born in 1988 in Kazan, then part of the Soviet Union; his family moved to Israel in 1990 and to Canada in 1996. He won gold medals at the International Mathematical Olympiad in 2003 and 2004 — with a perfect score the second time — entered the University of Toronto at 16, and graduated in mathematics after two years. He earned his PhD at Princeton in 2011 under Peter Sarnak.

After a Junior Fellowship at the Harvard Society of Fellows, he joined the University of Toronto in 2014, where he is now a full professor; he was the first faculty member of a Canadian university to win the Fields Medal.

Tsimerman's research sits at the meeting point of model theory and arithmetic geometry. The Pila–Wilkie counting theorem for o-minimal structures gave Diophantine geometry a new engine, and Tsimerman supplied many of the hard transcendence and Galois-theoretic inputs needed to run it: Ax–Lindemann theorems, the André–Oort conjecture for Siegel modular varieties (completed with Pila and Shankar), Ax–Schanuel for Shimura varieties with Mok and Pila, and Griffiths' conjecture on images of period maps with Bakker, Klingler and Brunebarbe. He received the SASTRA Ramanujan Prize in 2015, was elected a Fellow of the Royal Society in 2025, and received the Fields Medal in 2026.

Workplaces: University of Toronto

Canada

Award-winning work

Fields Medal 2026Tsimerman was awarded the medal for his contribution in recasting o-minimality as a fundamental method of arithmetic and complex algebraic geometry, and for his role in the proof of many central conjectures including Griffiths' conjecture on the algebraicity of images of period maps and the André–Oort conjecture for Siegel modular varieties. With Bakker, Klingler, Brunebarbe and others he placed period maps inside the o-minimal framework and extended the theory to a GAGA theorem over non-reduced complex spaces, proving Griffiths' long-standing conjecture. Carrying out the Pila–Zannier strategy, he proved Ax–Lindemann type functional transcendence results with Pila and supplied Galois lower bounds via the averaged Colmez conjecture, completing the André–Oort conjecture for Siegel modular varieties. With Mok and Pila he proved Ax–Schanuel for Shimura varieties, strengthening the functional-transcendence toolkit used in the Zilber–Pink conjecture.

Contributions, linked to the library

Library topicArithmetic geometryMade o-minimality a fundamental method of arithmetic geometry, proving the André–Oort conjecture for Siegel modular varieties and Griffiths' conjecture on period maps.Library topicModular formsHis André–Oort results describe the special subvarieties of Shimura and Siegel modular varieties, the moduli spaces of abelian varieties with extra symmetries.