About Galois reducibility of torsion cohomology classes for KHT Shimura varieties
Boyer, Pascal
arXiv, Tome 2019 (2019) no. 0, / Harvested from
We pursue the original strategy of my paper at JIMJ and we give a new criterion so that the localization of the cohomology of KHT Shimura variety is free. Precisely let $G$ be a similitude group with signatures $(1,d-1),(0,d),\cdots,(0,d)$ and $V_{\xi,\overline{\mathbb Z}_l}$ a local system associated to a fixed algebraic representation $\xi$ of $G(\mathbb Q)$. Consider a system $\mathfrak m$ of Hecke eigenvalues appearing in the free quotient of the cohomology group in middle degree of the Shimura variety $Sh_K$ associated to $G$ and with coefficients in $V_{\xi,\overline{\mathbb Z}_l}$. Then if the modulo $l$ galoisian representation $\overline \rho_{\mathfrak m}$ is irreducible of dimension $d$, and essentially if $l \geq d+1$, the localization at $\mathfrak m$ of every cohomology group of $Sh_K$ with coefficients in $V_{\xi,\overline{\mathbb Z}_l}$, is free.
Publié le : 2019-03-26
Classification:  Mathematics - Number Theory
@article{1903.10999,
     author = {Boyer, Pascal},
     title = {About Galois reducibility of torsion cohomology classes for KHT Shimura
  varieties},
     journal = {arXiv},
     volume = {2019},
     number = {0},
     year = {2019},
     language = {en},
     url = {http://dml.mathdoc.fr/item/1903.10999}
}
Boyer, Pascal. About Galois reducibility of torsion cohomology classes for KHT Shimura
  varieties. arXiv, Tome 2019 (2019) no. 0, . http://gdmltest.u-ga.fr/item/1903.10999/