Faces in rectilinear drawings of complete graphs

Fuente: arXiv
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Main Authors: Balko, Martin, Brötzner, Anna, Klute, Fabian, Tkadlec, Josef
Format: Preprint
Published: 2025
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author Balko, Martin
Brötzner, Anna
Klute, Fabian
Tkadlec, Josef
author_facet Balko, Martin
Brötzner, Anna
Klute, Fabian
Tkadlec, Josef
contents We initiate the study of extremal problems about faces in convex rectilinear drawings of~$K_n$, that is, drawings where vertices are represented by points in the plane in convex position and edges by line segments between the points representing the end-vertices. We show that if a convex rectilinear drawing of $K_n$ does not contain a common interior point of at least three edges, then there is always a face forming a convex 5-gon while there are such drawings without any face forming a convex $k$-gon with $k \geq 6$. A convex rectilinear drawing of $K_n$ is \emph{regular} if its vertices correspond to vertices of a regular convex $n$-gon. We characterize positive integers $n$ for which regular drawings of $K_n$ contain a face forming a convex 5-gon. To our knowledge, this type of problems has not been considered in the literature before and so we also pose several new natural open problems.
format Preprint
id arxiv_https___arxiv_org_abs_2507_00313
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Faces in rectilinear drawings of complete graphs
Balko, Martin
Brötzner, Anna
Klute, Fabian
Tkadlec, Josef
Combinatorics
Discrete Mathematics
We initiate the study of extremal problems about faces in convex rectilinear drawings of~$K_n$, that is, drawings where vertices are represented by points in the plane in convex position and edges by line segments between the points representing the end-vertices. We show that if a convex rectilinear drawing of $K_n$ does not contain a common interior point of at least three edges, then there is always a face forming a convex 5-gon while there are such drawings without any face forming a convex $k$-gon with $k \geq 6$. A convex rectilinear drawing of $K_n$ is \emph{regular} if its vertices correspond to vertices of a regular convex $n$-gon. We characterize positive integers $n$ for which regular drawings of $K_n$ contain a face forming a convex 5-gon. To our knowledge, this type of problems has not been considered in the literature before and so we also pose several new natural open problems.
title Faces in rectilinear drawings of complete graphs
topic Combinatorics
Discrete Mathematics
url https://arxiv.org/abs/2507.00313