Dear Katie, it's not clear from your message what you mean by "efficiently". You mean, a special function that can do it for you?
Here is one way to accomplish it: sgrp:=function(q,n0) local g, eij, i, j,n, d; eij:=function(i,j) local M; M:=IdentityMat(n,GF(q)); M[i][j]:=Z(q)^0; return M; end; g:=[]; n:=2*n0; for i in [1..n-1] do Add(g,eij(i+1,i)); d:=IdentityMat(n,GF(q)); d[i][i]:=Z(q); Add(g,d); od; for i in [1..n0-1] do Add(g,eij(i,i+1)); Add(g,eij(n0+i,n0+i+1)); od; return Group(g); end; Hope this helps, Dmitrii On 17 January 2011 12:21, Katie Morrison <kmorr...@gmail.com> wrote: > Hi all, I was wondering if there's an efficient way to create the subgroup > of GL(2n, q) consisting of block matrices of the form: > [A 0 > B C] > where A and C are in GL(n,q) and B is in M(n,q) (i.e. B is an arbitrary nxn > matrix). Thanks for the help. > > Katie > _______________________________________________ > Forum mailing list > Forum@mail.gap-system.org > http://mail.gap-system.org/mailman/listinfo/forum > -- Dmitrii Pasechnik ----- DISCLAIMER: Any text following this sentence does not constitute a part of this message, and was added automatically during transmission. CONFIDENTIALITY: This email is intended solely for the person(s) named and may be confidential and/or privileged. If you are not the intended recipient, please delete it, notify us and do not copy, use, or disclose its content. Thank you. Towards A Sustainable Earth: Print Only When Necessary _______________________________________________ Forum mailing list Forum@mail.gap-system.org http://mail.gap-system.org/mailman/listinfo/forum
