Takumi Murayama (January 22, 2021):  Grothendieck's localization problem
Channel: Algebraic Geometry at Stanford
Date: 2021-03-03

Let $f\colon Y \rightarrow X$  be a proper flat morphism of algebraic varieties. Grothendieck and Dieudonné showed that the smoothness of $f$ can be detected at closed points of $X$. Using André–Quillen homology, André showed that when $X$ is excellent, the same conclusion holds when $f$ is a closed flat morphism between locally noetherian schemes. We give a new proof of André's result using a version of resolutions of singularities due to Gabber. Our method gives a uniform treatment of Grothendieck's localization problem and resolves various new cases of this problem, which asks whether similar statements hold for other local properties of morphisms.