Triangle areas in line arrangements. (English) Zbl 1448.52019

Summary: A widely investigated subject in combinatorial geometry, originated from Erdős, is the following. Given a point set \(P\) of cardinality \(n\) in the plane, how can we describe the distribution of the determined distances? This has been generalized in many directions.
In this paper we propose the following variants. What is the maximum number of triangles of unit area, maximum area or minimum area, that can be determined by an arrangement of \(n\) lines in the plane?
We prove that the order of magnitude for the maximum occurrence of unit areas lies between \(\varOmega (n^2)\) and \(O(n^{9/ 4+\varepsilon})\), for every \(\varepsilon > 0\). This result is strongly connected to additive combinatorial results and Szemerédi-Trotter type incidence theorems. Next we show an almost tight bound for the maximum number of minimum area triangles. Finally, we present lower and upper bounds for the maximum area and distinct area problems by combining algebraic, geometric and combinatorial techniques.


52C30 Planar arrangements of lines and pseudolines (aspects of discrete geometry)
52C10 Erdős problems and related topics of discrete geometry
52A38 Length, area, volume and convex sets (aspects of convex geometry)
Full Text: DOI arXiv


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