Products of Commutators on a General Linear Group Over a Division Algebra

Resumo

The word maps \( \tilde{w}:\kern0.5em {\mathrm{GL}}_m{(D)}^{2k}\to {\mathrm{GL}}_n(D) \) and \( \tilde{w}:\kern0.5em {D}^{\ast 2k}\to {D}^{\ast } \) for a word \( w=\prod \limits_{i=1}^k\left[{x}_i,{y}_i\right], \) where D is a division algebra over a field K, are considered. It is proved that if \( \tilde{w}\left({D}^{\ast 2k}\right)=\left[{D}^{\ast },{D}^{\ast}\right], \) then \( \tilde{w}\left({\mathrm{GL}}_n(D)\right)\supset {E}_n(D)\backslash Z\left({E}_n(D)\right), \) where E_n(D) is the subgroup of GL_n(D), generated by transvections, and Z(E_n(D)) is its center. Furthermore if, in addition, n > 2, then \( \tilde{w}\left({E}_n(D)\right)\supset {E}_n(D)\backslash Z\left({E}_n(D)\right). \) The proof of the result is based on an analog of the “Gauss decomposition with prescribed semisimple part” (introduced and studied in two papers of the second author with collaborators) in the case of the group GL_n(D), which is also considered in the present paper.