Department of Mathematics


  •  Pavel Čoupek, MSU
  •  Ramification bounds for mod p étale cohomology via prismatic cohomology
  •  10/10/2022
  •  3:00 PM - 4:00 PM
  •  C304 Wells Hall
  •  Preston Wake (

Let $K/\bf{Q}_p$ be a local number field of absolute ramification index $e$, and let $X$ be a proper smooth $O_K$-scheme. I will discuss how one can obtain bounds on ramification of the mod $p$ Galois representations arising as the étale cohomology of (the geometric generic fiber of) $X$ in terms of $e$, the given prime $p>2$ and the cohomological degree $i$. The key tools for achieving this are the Breuil-Kisin and $A_{\rm inf}$-cohomology theories of Bhatt, Morrow and Scholze, and a series of conditions based on a criterion of Gee and Liu regarding crystallinity of the representation attached to a free Breuil-Kisin-Fargues $G_K$-module.



Department of Mathematics
Michigan State University
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C212 Wells Hall
East Lansing, MI 48824

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