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math.AG2022
Springer isomorphisms over a general base scheme
Sean Cotner
We establish the existence of Springer isomorphisms for reductive group schemes over general base schemes. For this, we first study centralizers of fiberwise regular sections of re…
math.AG2022
Lefschetz theorems in flat cohomology and applications
Sean Cotner, Bogdan Zavyalov
We prove a version of the Lefschetz hyperplane theorem for fppf cohomology with coefficients in any finite commutative group scheme over the ground field. As consequences, we estab…
math.AG2022★ 2 cited
Centralizers of sections of a reductive group scheme
Sean Cotner
This paper proves a number of flatness results for centralizers of sections of a reductive group scheme over a general base scheme. To this end, we establish relative versions of t…