Table of Contents
If $G$ is a group and $C\sbs G$ (i.e., a list of some elements of $G$), then we can produce the Cayley graph $X(G,C)$:
G = DihedralGroup(5) C = [G.gen(0), G.gen(1)] CG = G.cayley_graph( generators = C) CG.show() # not tested
The output is a directed graph, even if $C$ is inverse-closed; in the latter case we can convert $G$ to a graph by
CGU = CG.to_undirected() CGU.show() # not tested
Note that $C$ is not required to generate $G$. There are a number of keywords
to this command (for example, side
and simple
) but I cannot
follow their documentation and so I do not know what they do.
Note that the Graph()
command makes it easy to construct Cayley
graphs ourselves. For example, a cubelike graph is a Cayley
graph for $GF(2)^d$. We can construct them using Graph()
.
def cubelike(d, vector_list): VS = VectorSpace(GF(2),d) vxs = range(2^d) return Graph([vxs, lambda i,j: VS[i]-VS[j] in vector_list])
Here vector_list
is a list of 01-vectors of length $d$.
V = GF(2)^5 vl = [V([0,1,1,0,0]), V([1,1,0,1,1]), V([1,0,0,0,1])] T = cubelike(5, vl) show(T, layout='circular') # not tested
For a general group, we can use the following construction to create an undirected Cayley graph.
G = DihedralGroup(5) C = [G.gen(0), G.gen(0)^-1, G.gen(1), G.gen(1)^-1] CG = Graph( [ G.list(), lambda g, h: h*g^(-1) in C]) CG.show() # not tested
This will produce an incorrect result if $C$ is not inverse-closed.
Sage provides access to GAP, and hence access to any group that is in GAP or can be constructed in GAP. Be warned that the documentation for GAP probably outweighs that for Sage.