Erdős unit-distance problem (upper bound)
Openerdos-unit-distance-upper-bound
Statement
Let denote the maximum number of unordered pairs at distance exactly determined by points in the Euclidean plane . Erdős (1946) proved via a integer grid construction (and the May 2026 disproof of his upper-bound conjecture shows for infinitely many ). The best known upper bound is . \textbf{Task:} Improve the upper bound exponent below , or otherwise advance the asymptotic understanding of .
Current frontier
Upper bound due to Spencer-Szemerédi-Trotter (1984), unchanged for 40+ years; lower bound for infinitely many via the OpenAI / Sawin disproof of the original Erdős upper-bound conjecture (May 2026).
When this counts as solved
The current upper bound has stood for 40+ years. Closing this out means either pinning down the asymptotically tight value of with matching bounds, or making a strict advance: a rigorous proof that for some explicit , a lower bound strictly better than the from the 2026 disproof, or a structural impossibility theorem (e.g., a proven barrier that rules out an explicit class of approaches from breaking the exponent). A counterexample doesn't apply — this is a bound, not a binary conjecture. Refinements that don't move the exponent don't close the problem.
Classification
quantitative