On the k-planar local crossing number

TL;DR

This paper investigates the ratio of the local crossing number in k-planar graph decompositions, showing it scales as 1/k^2 under certain conditions, and provides bounds for total and maximum edge crossings.

Contribution

It establishes a relationship between the k-planar local crossing number and the 1-planar case, extending recent results and offering new bounds for crossings in graph drawings.

Findings

The ratio LCR_k(G)/LCR_1(G) is of order 1/k^2 under certain restrictions.

Existence of k-planar drawings with near-optimal total and maximum edge crossings.

Application of probabilistic tools like concentration inequalities and Lovász local lemma.

Abstract

Given a fixed positive integer $k$, the $k$-planar local crossing number of a graph $G$, denoted by $\text{LCR}_k(G)$, is the minimum positive integer $L$ such that $G$ can be decomposed into $k$ subgraphs, each of which can be drawn in a plane such that no edge is crossed more than $L$ times. In this note, we show that under certain natural restrictions, the ratio $\text{LCR}_k(G)/\text{LCR}_1(G)$ is of order $1/k^2$, which is analogous to a recent result of Pach et al. for the $k$-planar crossing number (defined as the minimum positive integer $C$ for which there is a $k$-planar drawing of $G$ with $C$ total edge crossings). As a corollary of our proof we show that, under similar restrictions, one may obtain a $k$-planar drawing of $G$ with \emph{both} the total number of edge crossings as well as the maximum number of times any edge is crossed essentially matching the best known bounds. Our proof relies on the crossing number inequality and several probabilistic tools such as concentration of measure and the Lov\'asz local lemma.