[GAP Forum] Semidirect products

Sandeep Murthy sandeepr.murthy at gmail.com
Tue Oct 4 15:57:50 BST 2011


Dear GAP Forum members,

is there a quick way to directly access the factors of a semidirect product group?

I have constructed a semidirect product G = N \rtimes_\theta P, where P, N are groups,
where P acts on N via a homomorphism \theta: P \longrightarrow Aut(N).  How can I 
define the subgroups of G isomorphic to N and to P?  

I have tried to construct these as N \rtimes_\theta_0 { 1}, and {1} \rtimes_\theta_0 P, 
where \theta_0 : P \longrightarrow Aut(N) is trivial, but on GAP they are not subgroups 
of G.

Sincerely, Sandeep.






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