ASKSAGE: Sage Q&A Forum - RSS feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Tue, 20 Nov 2018 20:06:56 +0100Orbits on group actions acting on setshttps://ask.sagemath.org/question/9652/orbits-on-group-actions-acting-on-sets/Hello!
I am wondering how to solve the following problem efficiently.
I have a Permuation Group $G$ acting on $A = \{1,\ldots,n\}$ and I wish to compute the orbits of $G$ but not the ones of $G$ acting on $A$ but rather for $G$ acting on some $S \subseteq A \times A$ in the natural way. That is if $g \in G$ and $ x = \{a,b\} \in S$ then $x^g = {a^g,b^g\} \in S$
Other software for permuation groups (magma, gap) allows to do this by specifing an additional option "on sets/on tuples" to compute the specifed orbits.
I am wondering how could I do the same in sage, given a permuation group $G$ and an $S$ as described above.
Thanks!SGQWed, 26 Dec 2012 10:56:11 +0100https://ask.sagemath.org/question/9652/Determining if two subgroups of a symmetric group are conjugatehttps://ask.sagemath.org/question/44357/determining-if-two-subgroups-of-a-symmetric-group-are-conjugate/If I have two particular subgroups of a symmetric group, is there any built-in way in Sage to determine if the groups are conjugate to one another? I tried creating a `ConjugacyClass` for each and then comparing them, but this gives an error:
S = SymmetricGroup(3)
gen1 = Permutation('(1,2,3)')
gen2 = Permutation('(1,3,2)')
gen3 = Permutation('(1,2)')
gen4 = Permutation('(1,3)')
G1 = PermutationGroup([gen1, gen3])
G2 = PermutationGroup([gen2, gen4])
ConjugacyClass(S, G1) == ConjugacyClass(S, G2)
When executing the very last line I get the error
TypeError: For implementing multiplication, provide the method '_mul_' for (1,2) resp. Permutation Group with generators [(1,2), (1,2,3)]
cjohnsonTue, 20 Nov 2018 20:06:56 +0100https://ask.sagemath.org/question/44357/does as_permutation_group() respect generators?https://ask.sagemath.org/question/40927/does-as_permutation_group-respect-generators/From sage documentation I can construct a group as follows:
sage: m1 = matrix(GF(11), [[1,2],[3,4]])
sage: m2 = matrix(GF(11), [[1,3],[10,0]])
sage: G = MatrixGroup(m1, m2); G
Matrix group over Finite Field of size 11 with 2 generators (
[1 2] [ 1 3]
[3 4], [10 0]
)
Now I use the following code:
sage: G_p=G.as_permutation_group(); G_p
Permutation Group with generators [(1,2,3,4,5,6,7,8,9,10,11)(12,13,15,14,16)(17,18), (1,3,5,7,9,11,2,4,6,8,10)(12,14,13,16,15)(17,18)]
In this case it is true that the generators of G are in correspondence with the generators of G_p. Is this always the case? I mean, if I compute a very complicated group G with lots of generators and its corresponding permutation group G_p, then is it true that G.gens()[i] corresponds to G_p.gens[i]?amontero90Thu, 01 Feb 2018 20:20:47 +0100https://ask.sagemath.org/question/40927/Permutation Representations and the Modular Grouphttps://ask.sagemath.org/question/9202/permutation-representations-and-the-modular-group/Hi!
Given a congruence subgroup of the modular group G = SL2Z, how can one use Sage to find the permutation representations of G on the cosets of each of those normal subgroups? Specifically I am looking at the subgroups on page 22 here: http://arxiv.org/pdf/1201.3633v2.pdf
Many thanks!
JimereeFri, 03 Aug 2012 11:19:42 +0200https://ask.sagemath.org/question/9202/