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11 votes
3 answers
409 views

Two disjoint trees

Let $G$ be a graph and let $A_1, A_2 \subseteq V(G)$ be disjoint sets of vertices. Let us call $(A_1, A_2)$ independent if there exist vertex-disjoint trees $T_1, T_2 \subseteq G$ within $G$ which ...
monkeymaths's user avatar
  • 1,169
9 votes
0 answers
499 views

A separation property of graphs of bounded tree-width

The following separation property of trees is well-known and in fact easy to prove (see e.g. the paper "Covering a hypergraph of subgraphs" by Noga Alon, Lemma 2.2) Let $T$ be a tree and $r, m$ non-...
monkeymaths's user avatar
  • 1,169
2 votes
1 answer
181 views

What is the relation between size of maximum clique and branchwidth?

Let $bw(G)$ be the branchwidth of graph $G$ and $\omega(G)$ be the size of maximum clique in $G$. I think the following inequality holds: $$ \omega(G)\leq bw(G) $$ Intuition: Assume (in reverse of ...
Omid Ebrahimi's user avatar
2 votes
1 answer
302 views

A variant of Kruskal's theorem

For $X$ and $Y$ finite sequences of finite trees, let us say that $X$ is everywhere contained in $Y$ ($X\subseteq_{ec}Y$) iff, for every $y\in Y$, there is some $x\in X$ such that $x$ is a minor of $y$...
M Carl's user avatar
  • 365