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k-arrangements of pseudolines and pseudocircles
Abstract
A k-arrangement of pseudolines is a set of bi-infinite curves in the plane such that any two of them intersect each other in exactly k points, at which they cross, and it is simple if no three curves meet at a common point. Cyclic arrangements are the only simple $1$-arrangements of pseudolines that are unavoidable, in the Ramsey spirit: for each fixed m≥ 1, every sufficiently large simple $1$-arrangement of pseudolines has a cyclic subarrangement of size m. We show that, for every m≥ 3, the number of unavoidable simple k-arrangements of pseudolines of size m grows exponentially with k, independently of m. For even k, we prove an analogous result for k-arrangements of pseudocircles.
Related
BibTeX
@misc{kyncl2026karrangements,
title = {{$k$-arrangements of pseudolines and pseudocircles}},
author = {Jan Kynčl and Carolina Medina and Gelasio Salazar},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.00773},
eprint = {2610.00773},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.00773},
}
RIS
TY - UNPB
TI - k-arrangements of pseudolines and pseudocircles
AU - Jan Kynčl
AU - Carolina Medina
AU - Gelasio Salazar
PY - 2026
DA - 2026/10/01
PB - arXiv
DO - 10.48550/arxiv.2610.00773
UR - https://arxiv.org/abs/2610.00773
AB - A k-arrangement of pseudolines is a set of bi-infinite curves in the plane such that any two of them intersect each other in exactly k points, at which they cross, and it is simple if no three curves meet at a common point. Cyclic arrangements are the only simple $1$-arrangements of pseudolines that are unavoidable, in the Ramsey spirit: for each fixed m≥ 1, every sufficiently large simple $1$-arrangement of pseudolines has a cyclic subarrangement of size m. We show that, for every m≥ 3, the number of unavoidable simple k-arrangements of pseudolines of size m grows exponentially with k, independently of m. For even k, we prove an analogous result for k-arrangements of pseudocircles.
ER -