Dear GAP-Forum,
On Mar 16, 2006, at 5:58 AM, Robert Heffernan wrote:
I do have a followup question, if anybody can help.
I have created a finitely presented group G
F:=FreeGroup("a","b","c","d");;a:=F.1;;b:=F.2;;c:=F.3;;d:=F.
4;;rels:= <some words in terms of a,b,c and d>G:=F/rels;a:=G.
1;;b:=G.2;;c:=G.3;;d:=G.4;;
I have then created a new set of words/relations, rels2 say, in
termsof a,b,c and d (by calculating with things in G).
Now I want to create a new finitely presented group in a manner
such as this:H:=F/rels2;
However, I can't do this directly as a,b,c and d are now elements
of G, not F.
I can't find a simple way to relate a,b,c and d back to the
generatorsof the free group F,
You have three options. In order from ``cleanest'' to ``most
technical'':
a) From a `GroupHomomorphismByImages' from F to G, mapping F.i to
G.i. Then take the `PreImagesRepresentative' of your words.
b) Use `MappedWord' to map a word in the G.i to a word in the F.i
c) For any element of G, `UnderlyingElement' returns the
corresponding element of F, i.e. the relators you want.
Best wishes,
Alexander Hulpke
-- Colorado State University, Department of Mathematics,
Weber Building, 1874 Campus Delivery, Fort Collins, CO 80523-1874, USA
email: [EMAIL PROTECTED], Phone: ++1-970-4914288
http://www.math.colostate.edu/~hulpke
_______________________________________________
Forum mailing list
[email protected]
http://mail.gap-system.org/mailman/listinfo/forum
