[GAP Forum] "generalized centralizer question

[Walter Becker]

I am interested in calculating the set of elements (group) which commute with a given non-abelian subgroup of a group. 
 
The problem can be illustrated by a simple example.
Consider the group 
[C_(9} @ C_3] @ D_4 = G
 
The group D_4 acts on the 3-group by an operator of order 2 (say here the C_2 element in D_4).  What I want to do is to calculate the "normal subgroup" [C_9 @ C_3 X C_4] and then form the quotient group 
Q = G/[C_9 at C_3 X C_4]
 
Here the quotient is obviously C_2. But the interest is in more general cases with a non-abelian normal p-subgroup. (The case when the p-group is abelian can be done with the centralizer command.)
 
Comments 
 
Thank you
 
Walter Becker
 
 
_________________________________________________________________
Making the world a better place one message at a time.
http://www.imtalkathon.com/?source=EML_WLH_Talkathon_BetterPlace