English

Group theoretical independence of $\ell$-adic Galois representations

Algebraic Geometry 2017-01-18 v1

Abstract

Let K/QK/\mathbb{Q} be a finitely generated field of characteristic zero and X/KX/K a smooth projective variety. Fix qNq\in\mathbb{N}. For every prime number \ell let ρ\rho_\ell be the representation of Gal(K)\mathrm{Gal}(K) on the \'etale cohomology group Hq(XK,Q)H^q(X_{\overline{K}}, \mathbb{Q}_\ell). For a field kk we denote by kabk_{\mathrm{ab}} its maximal abelian Galois extension. We prove that there exist finite Galois extensions k/Qk/\mathbb{Q} and F/KF/K such that the restricted family of representations (ρGal(kabF))(\rho_\ell|\mathrm{Gal}(k_{\mathrm{ab}} F))_\ell is group theoretically independent in the sense that ρ1(Gal(kabF))\rho_{\ell_1}(\mathrm{Gal}(k_{\mathrm{ab}} F)) and ρ2(Gal(kabF))\rho_{\ell_2}(\mathrm{Gal}(k_{\mathrm{ab}} F)) do not have a common finite simple quotient group for all prime numbers 12\ell_1\neq \ell_2.

Keywords

Cite

@article{arxiv.1701.04757,
  title  = {Group theoretical independence of $\ell$-adic Galois representations},
  author = {Sebastian Petersen},
  journal= {arXiv preprint arXiv:1701.04757},
  year   = {2017}
}