Pach's conjecture on tangencies among precisely 1-intersecting curves

Let a family of planar curves be precisely 1-intersecting if every pair of curves has precisely one common point, either a crossing or a tangency, and assume that no three curves share a common point. Pach's conjecture. Every family of nn precisely 11-intersecting planar curves in which no three curves share a common point admits O(n)O(n) tangencies.

This conjecture concerns the extremal number of tangencies in arrangements of pseudo-segments. It was settled by the authors for xx-monotone curves, while the general case stated here is resolved according to the supplied status.

Sources & referencesView supporting material

Primary source

Eyal Ackerman and Balázs Keszegh, “On the maximum number of tangencies among 1-intersecting curves”, arXiv:2603.11885 (2026).

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