English

Inducing Super-Approximation

Group Theory 2018-02-13 v1 Number Theory

Abstract

Let Γ2Γ1\Gamma_2\subseteq \Gamma_1 be finitely generated subgroups of GLn0(Z[1/q0]){\rm GL}_{n_0}(\mathbb{Z}[1/q_0]). For i=1i=1 or 22, let Gi\mathbb{G}_i be the Zariski-closure of Γi\Gamma_i in (GLn0)Q({\rm GL}_{n_0})_{\mathbb{Q}}, Gi\mathbb{G}_i^{\circ} be the Zariski-connected component of Gi\mathbb{G}_i, and let GiG_i be the closure of Γi\Gamma_i in pq0GLn0(Zp)\prod_{p\nmid q_0}{\rm GL}_{n_0}(\mathbb{Z}_p). In this article we prove that, if G1\mathbb{G}_1^{\circ} is the smallest closed normal subgroup of G1\mathbb{G}_1^{\circ} which contains G2\mathbb{G}_2^{\circ} and Γ2G2\Gamma_2\curvearrowright G_2 has spectral gap, then Γ1G1\Gamma_1\curvearrowright G_1 has spectral gap.

Keywords

Cite

@article{arxiv.1802.03561,
  title  = {Inducing Super-Approximation},
  author = {Alireza Salehi Golsefidy and Xin Zhang},
  journal= {arXiv preprint arXiv:1802.03561},
  year   = {2018}
}
R2 v1 2026-06-23T00:17:51.794Z