Conference on Arithmetic Geometry in honor of Luc Illusie

Collection Conference on Arithmetic Geometry in honor of Luc Illusie

Organizer(s) Lei Fu (Tsinghua University), Fabrice Orogozo (CNRS&IMJ-PRG), Weizhe Zheng (MCM, AMSS, CAS)
Date(s) 6/7/21 - 6/11/21
00:00:00 / 00:00:00
3 22

Grothendieck–Serre in the quasi-split unramified case

By Kęstutis Česnavičius

The Grothendieck–Serre conjecture predicts that every generically trivial torsor under a reductive group scheme G over a regular local ring R is trivial. We settle it in the case when G is quasi-split and R is unramified. To overcome obstacles that have so far kept the mixed characteristic case out of reach, we adapt Artin's construction of "good neighborhoods" to the setting where the base is a discrete valuation ring, build equivariant compactifications of tori over higher dimensional bases, and study the geometry of the affine Grassmannian in bad characteristics.

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