i think i see what is going on. By reducing the number of vertices plotted, it appears that the "double edges" are really little clusters of four edges!
On 13 mar, 21:27, Pierre <pierre.guil...@gmail.com> wrote: > Dear Tom, > > Thanks for your answer! I get the empty set, too. I really wonder what > is going on with the picture though... if one cannot "rely on the > picture", then it pretty much defeats the purpose when it comes to > Cayley graphs, doesn't it? > > and i mean, there *is* a double arrow on some edges. > > thanks again, > pierre > > On 13 mar, 13:50, Tom Boothby <tomas.boot...@gmail.com> wrote: > > > > > > > > > Pierre, > > > Don't rely on the picture! > > > sage: U = set(gr.edges()) > > sage: V = set(gr.reverse().edges()) > > sage: U.intersection(V) #for me, this is the empty set > > > On Tue, Mar 13, 2012 at 3:26 AM, Pierre <pierre.guil...@gmail.com> wrote: > > > Hi, > > > > I've been playing with Cayley graphs in Sage (thanks to whoever > > > implemented this!) I got funny results on one example, and I'd like to > > > understand. > > > > I've tried SL(2, ZZ): > > > > sage: G= SL(2, ZZ) > > > sage: S, T= G.gens(); ST= S*T > > > sage: L= [S^i*ST^j for i in range(4) for j in range(3)] #S has order > > > 4, ST has order 3 > > > sage: els= Set([ a*b*c*d for a in L for b in L for c in L for d in L]) > > > sage: gr= G.cayley_graph(generators = [S, ST], elements= els) > > > sage: gr.show(color_by_label= True, iterations= 500, vertex_labels= > > > False, vertex_size= 1, dpi= 800)) #for example > > > > I don't know how to attach a picture to this message, so I'll have to > > > describe the result as very close to the Cayley graph of PSL(2, ZZ) > > > rather than SL(2, ZZ)!! it looks as if one of my generators has order > > > 2!! > > > > does anyone know what is going on? > > > > thanks! > > > Pierre > > > > -- > > > To post to this group, send email to sage-support@googlegroups.com > > > To unsubscribe from this group, send email to > > > sage-support+unsubscr...@googlegroups.com > > > For more options, visit this group > > > athttp://groups.google.com/group/sage-support > > > URL:http://www.sagemath.org -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
