Exactness property of Breuil-Kisin functors and Bloch-Kato Selmer groups

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Hauptverfasser: Čoupek, Pavel, Gazaki, Evangelia, Marmora, Adriano
Format: Preprint
Veröffentlicht: 2026
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author Čoupek, Pavel
Gazaki, Evangelia
Marmora, Adriano
author_facet Čoupek, Pavel
Gazaki, Evangelia
Marmora, Adriano
contents Let $K$ be a $p$-adic field and $T$ a lattice in a semistable representation of $\mathrm{Gal}(\overline{K}/K)$ with Hodge-Tate weights in $[0, r]$. Assuming $0\leq r<p-1$, we prove that for a semistable extension of $\mathbb{Z}_p$ by $T$, the corresponding sequence of strongly divisible modules is exact. The same statement is proved for Breuil-Kisin modules for all $r\geq 0$. In the crystalline case, we deduce that the integral Bloch-Kato Selmer group $H^1_f(K, T)$ is computed by $\mathrm{Ext}^1$ in the category of crystalline strongly divisible modules. Using further exactness results, we define a tensor product of strongly divisible modules, which commutes with the functors to Galois representations. As an application, we show that for abelian varieties $A_1, A_2$ over $K$ with good reduction, the cup product map $δ_1\cupδ_2:A_1(K)\otimes A_2(K)\rightarrow H^2(K, T_p(A_1)\otimes T_p(A_2))$ induced by the Kummer sequences of $A_1, A_2$ factors through an $\mathrm{Ext}^2$ group of strongly divisible modules.
format Preprint
id arxiv_https___arxiv_org_abs_2603_26035
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Exactness property of Breuil-Kisin functors and Bloch-Kato Selmer groups
Čoupek, Pavel
Gazaki, Evangelia
Marmora, Adriano
Number Theory
Algebraic Geometry
11S25, 11F80, 14F20, 14F30
Let $K$ be a $p$-adic field and $T$ a lattice in a semistable representation of $\mathrm{Gal}(\overline{K}/K)$ with Hodge-Tate weights in $[0, r]$. Assuming $0\leq r<p-1$, we prove that for a semistable extension of $\mathbb{Z}_p$ by $T$, the corresponding sequence of strongly divisible modules is exact. The same statement is proved for Breuil-Kisin modules for all $r\geq 0$. In the crystalline case, we deduce that the integral Bloch-Kato Selmer group $H^1_f(K, T)$ is computed by $\mathrm{Ext}^1$ in the category of crystalline strongly divisible modules. Using further exactness results, we define a tensor product of strongly divisible modules, which commutes with the functors to Galois representations. As an application, we show that for abelian varieties $A_1, A_2$ over $K$ with good reduction, the cup product map $δ_1\cupδ_2:A_1(K)\otimes A_2(K)\rightarrow H^2(K, T_p(A_1)\otimes T_p(A_2))$ induced by the Kummer sequences of $A_1, A_2$ factors through an $\mathrm{Ext}^2$ group of strongly divisible modules.
title Exactness property of Breuil-Kisin functors and Bloch-Kato Selmer groups
topic Number Theory
Algebraic Geometry
11S25, 11F80, 14F20, 14F30
url https://arxiv.org/abs/2603.26035