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Erdős Degeneracy Conjecture


The Erdős degeneracy conjecture asserted that every fixed bipartite graph H having graph degeneracy at most r satisfies

 ex(n,H)=O(n^(2-1/r)),

where ex(n,H) is the largest number of edges in an n-vertex graph containing no copy of H as a subgraph, and O is big-O notation.

An AI-generated proof given by OpenAI (2026) disproved the conjecture already for r=2. It constructs a fixed connected bipartite graph H with graph degeneracy at most 2 and constants c,epsilon>0 such that

 ex(n,H)>=cn^(3/2+epsilon)

for all sufficiently large n. This also disproves the forward implication of the related conjecture that a bipartite graph H has graph degeneracy at most 2 if and only if ex(n,H)=O(n^(3/2)) (Erdős 1981).


See also

Bipartite Graph, Erdős-Simonovits Compactness Conjecture, Extremal Graph Theory, Graph Degeneracy, Subgraph

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References

Erdős, P. "Some Recent Results on Extremal Problems in Graph Theory." In Theory of Graphs (International Symposium, Rome, 1966). New York: Gordon and Breach, pp. 117-123, 1967.Erdős, P. "Problems and Results in Graph Theory." In The Theory and Applications of Graphs (Kalamazoo, 1980). New York: Wiley, pp. 331-341, 1981. https://www.renyi.hu/~p_erdos/1981-20.pdf.OpenAI. "Counterexamples to the Compactness and Degeneracy Conjectures for Extremal Numbers." Ch. 10 in Ten Advances in Mathematics and Theoretical Computer Science. Aug. 1, 2026. https://cdn.openai.com/pdf/ten-proofs-oai.pdf.

Cite this as:

Weisstein, Eric W. "Erdős Degeneracy Conjecture." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/ErdosDegeneracyConjecture.html

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