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Feb
10
comment Isomorphic but not equivalent actions of a group G
@RobArthan Some lectures notes from a class I have.
Feb
10
asked Isomorphic but not equivalent actions of a group G
Feb
10
comment Graph Theory Function (Thomassen)
Btw doesn't the claim follows quickly from 1 and 2? By lemma $2$ you get a minor with large average degree provided that your graph has large girth. By picking a suitably large girth , the min degree is then large enough so that the average degree satisfies the conditions of lemma 1 giving you the desired complete graph as a minor. Where exactly do you get stuck?
Feb
10
comment Graph Theory Function (Thomassen)
@Lindsey I have a recollection of seeing this thing proven in Diestel's book.
Feb
8
answered Prove that for every connected graph $G$ of order $n$ and diameter $d$ , $\chi(G)\leq n-d+1$
Feb
7
comment A question about the interlacing of symmetric matrices (graph interlacing)
Hm.. that makes sense, thanks!
Feb
7
comment A question about the interlacing of symmetric matrices (graph interlacing)
Chris, do you happen to see a (efficient) way to use this relation in order to compute the eigenvalues of $B$ given that the eigenvalues of $A$ are known?
Feb
5
comment Permutation isomorphic subgroups of $S_n$ are conjugate
That does it, thanks.
Feb
5
accepted Permutation isomorphic subgroups of $S_n$ are conjugate
Feb
4
asked Permutation isomorphic subgroups of $S_n$ are conjugate
Feb
1
revised What are $r(\Lambda)$ and $s(\Lambda)$?
edited body
Feb
1
answered What are $r(\Lambda)$ and $s(\Lambda)$?
Jan
29
comment Adding an edge and a vertex to non-isomorphic graphs
@chowching Yes in that case you are right.
Jan
29
comment Adding an edge and a vertex to non-isomorphic graphs
Intuitively, two vertices are in the same orbit if they are "indistinguishable" in other words any isomorphism from $G$ to $H$ only can map a vertex to vertices in the same orbit.
Jan
29
comment Adding an edge and a vertex to non-isomorphic graphs
Its not necessarily the union. Take $G = H$ to be the Petersen graph. Then $Aut(G\cup H)$ only has 1 orbit.
Jan
29
revised Adding an edge and a vertex to non-isomorphic graphs
added 9 characters in body
Jan
29
answered Adding an edge and a vertex to non-isomorphic graphs
Jan
20
answered Graph Theory Software with simple GUI
Jan
19
comment Can we say anything about the order of the second largest eigen-value?
You should then try to figure something out of the formula for the eigenvalues of a vt graph. Note that in general vertex transitive does not give you much of a difference. There are pairs of vertex transitive and not vertex transitive regular graphs with the same value of your expression.
Jan
19
answered Can we say anything about the order of the second largest eigen-value?