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Problem #807: The bipartition number $\tau(G)$ of a graph $G$ is the...

The bipartition number $\tau(G)$ of a graph $G$ is the smallest number of pairwise edge disjoint complete bipartite graphs whose union is $G$. The...

Problem Statement

The bipartition number $\tau(G)$ of a graph $G$ is the smallest number of pairwise edge disjoint complete bipartite graphs whose union is $G$. The independence number $\alpha(G)$ is the size of the largest independent subset of $G$.

Is it true that, if $G$ is a random graph on $n$ vertices with edge probability $1/2$, then\[\tau(G)=n-\alpha(G)\]almost surely?
Categories: Graph Theory

Progress

Alon [Al15] showed this is false: in fact almost surely $\tau(G) \leq n-\alpha(G)-1$. Alon, Bohman, and Huang [ABH17] proved that in fact there is some absolute constant $c>0$ such that almost surely\[\tau(G) \leq n-(1+c)\alpha(G).\]

Source: erdosproblems.com/807 | Last verified: January 16, 2026

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