combinatorics / Graph theory

Erdős Problem #74: locally almost bipartite graphs of infinite chromatic number

Astra proves that there exists a divergent function f:NN,f(n), f:\mathbb N\to\mathbb N,\qquad f(n)\to\infty, such that no graph GG of infinite chromatic number can satisfy dbip(H)f(n) d_{\mathrm{bip}}(H)\le f(n) for every finite nn-vertex subgraph HGH\subseteq G, where dbip(H)d_{\mathrm{bip}}(H) is the minimum number of edges that must be deleted to make HH bipartite. In fact, every included resolution proves the stronger statement that graphs satisfying the constructed local bound are 3-colorable. The formal challenge advertises only the weaker conclusion that their chromatic number must be finite.

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combinatoricsAug 28, 2026Significance 38/100Registry: lean verified

Erdős Problem #74: locally almost bipartite graphs of infinite chromatic number

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Astra proves that there exists a divergent function f:NN,f(n), f:\mathbb N\to\mathbb N,\qquad f(n)\to\infty, such that no graph GG of infinite chromatic number can satisfy dbip(H)f(n) d_{\mathrm{bip}}(H)\le f(n) for every finite nn-vertex subgraph HGH\subseteq G, where dbip(H)d_{\mathrm{bip}}(H) is the minimum number of edges that must be deleted to make HH bipartite. In fact, every included resolution proves the stronger state…

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Astra proves that there exists a divergent function f:NN,f(n), f:\mathbb N\to\mathbb N,\qquad f(n)\to\infty, such that no graph GG of infinite chromatic number can satisfy dbip(H)f(n) d_{\mathrm{bip}}(H)\le f(n) for every finite nn-vertex subgraph HGH\subseteq G, where dbip(H)d_{\mathrm{bip}}(H) is the minimum number of edges that must be deleted to make HH bipartite. In fact, every included resolution proves the stronger statement that graphs satisfying the constructed local bound are 3-colorable. The formal challenge advertises only the weaker conclusion that their chromatic number must be finite.

Astra proves that there exists a divergent function f:NN,f(n), f:\mathbb N\to\mathbb N,\qquad f(n)\to\infty, such that no graph GG of infinite chromatic number can satisfy dbip(H)f(n) d_{\mathrm{bip}}(H)\le f(n) for every finite nn-vertex subgraph HGH\subseteq G, where dbip(H)d_{\mathrm{bip}}(H) is the minimum number of edges that must be deleted to make HH bipartite. In fact, every included resolution proves the stronger statement that graphs satisfying the constructed local bound are 3-colorable. The formal challenge advertises only the weaker conclusion that their chromatic number must be finite.

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