01 · A life in mathematics
The person behind the work
Alessio Figalli was born in Rome and trained in Italy and France. He was a professor at ETH Zurich, which he joined in 2016, when awarded the 2018 Fields Medal. His research centers on optimal transport, the mathematical study of moving one distribution of mass into another at minimum cost. He uses this framework to study nonlinear partial differential equations, geometric inequalities and the regularity of solutions. A central achievement is understanding when transport maps and the equations they satisfy remain well behaved despite rough data or singularities. His work connects abstract optimization with the fine structure of shapes and evolving systems.
The contribution, explained
Imagine reshaping one pile of sand into another while minimizing the total transportation cost. Optimal transport turns this picture into a precise problem for probability measures or mass distributions. A cheapest transport plan may exist, but existence alone does not tell us whether the movement is smooth or has sudden discontinuities. Figalli developed tools to understand such regularity questions and the nonlinear equations behind them, notably the Monge–Ampère equation. He also connected transport with sharp geometric inequalities and their stability: if a shape almost achieves an optimal bound, how close must it be to an ideal shape?
Why it matters
Transport becomes a versatile method for studying nonlinear equations, geometric shapes and probability distributions. Figalli’s results clarify when optimal behavior has stable, regular structure and when singularities or nearly optimal configurations require subtler analysis.