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Feb
17
answered Finding the spanning subgraphs of a complete bipartite graph
Feb
15
revised Prove that for every connected graph $G$ of order $n$ and diameter $d$ , $\chi(G)\leq n-d+1$
deleted 69 characters in body
Feb
15
comment Prove that for every connected graph $G$ of order $n$ and diameter $d$ , $\chi(G)\leq n-d+1$
@ctlaltdefeat Good point. Edited my answer.
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