Subgroups of the General Linear Group That Contain Elementary Subgroup Over a Rank 2 Commutative Ring Extension

Abstract

Let R = $$ \prod \limits_{i\in I}{F}_i $$ be the direct product of fields, and let $$ S=R\left[\sqrt{d}\right]=\prod \limits_{i\in I}{F}_i\left[\sqrt{d_i}\right] $$ be a rank 2 extension of R. The subgroups of the general linear group GL(2n,R), n ≥ 3, that contain the elementary group E (n, S) are described. It is shown that for every such a subgroup H there exists a unique ideal A ⊴ R such that E (n, S)E(2n,R,A) ≤ H ≤ NGL(2n,R) (E (n, S)E(2n,R,A)).