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A graph is IC-planar if it admits a drawing in the plane with at most one crossing per edge and such that two pairs of crossing edges share no common end vertex. IC-planarity specializes both NIC-planarity, which allows a pair of crossing…

Discrete Mathematics · Computer Science 2017-07-28 Christian Bachmaier , Franz J. Brandenburg , Kathrin Hanauer

A \emph{$k$-planar graph} is a graph that can be drawn in the plane such that every edge is crossed at most $k$ times. For $k \leq 4$, Pach and T\'oth proved a bound of $(k+3)(n-2)$ on the total number of edges of a $k$-planar graph, which…

Computational Geometry · Computer Science 2016-08-31 Michael A. Bekos , Michael Kaufmann , Chrysanthi N. Raftopoulou

A topological graph is a graph drawn in the plane. A topological graph is $k$-plane, $k>0$, if each edge is crossed at most $k$ times. We study the problem of partitioning the edges of a $k$-plane graph such that each partite set forms a…

A multigraph drawn in the plane is non-homotopic if no two edges connecting the same pair of vertices can be continuously deformed into each other without passing through a vertex, and is $k$-crossing if every pair of edges…

Combinatorics · Mathematics 2024-01-22 António Girão , Freddie Illingworth , Alex Scott , David R. Wood

Topological drawings are representations of graphs in the plane, where vertices are represented by points, and edges by simple curves connecting the points. A drawing is simple if two edges intersect at most in a single point, either at a…

Computational Geometry · Computer Science 2022-09-08 Alfredo García , Alexander Pilz , Javier Tejel

A graph is called a $k$-planar unit distance graph if it can be drawn in the plane such that every edge is a unit line segment and is involved in at most $k$ crossings. We investigate $u_k(n)$, the maximum number of edges of such graphs on…

Combinatorics · Mathematics 2026-03-23 Panna Gehér , Dömötör Pálvölgyi , Dániel G. Simon , Géza Tóth

A graph drawn on the plane is called $1$-plane if each edge is crossed at most once by another edge. In this paper, we show that every $4$-connected $1$-plane graph has a connected spanning plane subgraph. We also show that there exist…

Combinatorics · Mathematics 2024-04-09 Kenta Noguchi , Katsuhiro Ota , Yusuke Suzuki

Every finite graph admits a \emph{simple (topological) drawing}, that is, a drawing where every pair of edges intersects in at most one point. However, in combination with other restrictions simple drawings do not universally exist. For…

Computational Geometry · Computer Science 2020-08-26 Michael Hoffmann , Chih-Hung Liu , Meghana M. Reddy , Csaba D. Tóth

We explore various techniques for counting the number of straight-edge crossing-free graphs that can be embedded on a planar point set. In particular, we derive a lower bound on the ratio of the number of such graphs with $m+1$ edges to the…

Combinatorics · Mathematics 2019-05-24 Siddharth Prasad

A star-simple drawing of a graph is a drawing in which adjacent edges do not cross. In contrast, there is no restriction on the number of crossings between two independent edges. When allowing empty lenses (a face in the arrangement induced…

Computational Geometry · Computer Science 2020-08-26 Stefan Felsner , Michael Hoffmann , Kristin Knorr , Irene Parada

A connected topological drawing of a graph divides the plane into a number of cells. The type of a cell $c$ is the cyclic sequence of crossings and vertices along the boundary walk of $c$. For example, all triangular cells with three…

Combinatorics · Mathematics 2026-03-10 Benedikt Hahn , Torsten Ueckerdt , Birgit Vogtenhuber

A graph is 1-planar if it can be drawn in the plane such that each edge is crossed at most once. A graph, together with a 1-planar drawing is called 1-plane. Brandenburg et al. showed that there are maximal 1-planar graphs with only…

Combinatorics · Mathematics 2015-09-21 János Barát , Géza Tóth

A 1-planar graph refers to a graph that can be drawn on the plane such that each edge has at most one crossing. In this paper, focusing on the spectral Tur\'{a}n-type problems of $1$-planar graphs, we determine completely the unique…

Combinatorics · Mathematics 2025-12-16 Weilun Xu , An Chang

We study straight-line drawings of planar graphs with few segments and few slopes. Optimal results are obtained for all trees. Tight bounds are obtained for outerplanar graphs, 2-trees, and planar 3-trees. We prove that every 3-connected…

Combinatorics · Mathematics 2008-09-09 Vida Dujmovic' , David Eppstein , Matthew Suderman , David R. Wood

Given a family of graphs $\mathcal{F}$, a graph $G$ is $\mathcal{F}$-saturated if it is $\mathcal{F}$-free but the addition of any missing edge creates a copy of some $F \in \mathcal{F}$. The study of the minimum number of edges in…

Combinatorics · Mathematics 2025-11-18 Xiaoteng Zhou , Kazuya Haraguchi , Hanchun Yuan

We investigate straight-line drawings of topological graphs that consist of a planar graph plus one edge, also called almost-planar graphs. We present a characterization of such graphs that admit a straight-line drawing. The…

Computational Geometry · Computer Science 2015-07-01 Peter Eades , Seok-Hee Hong , Giuseppe Liotta , Naoki Katoh , Sheung-Hung Poon

A drawing of a graph is fan-planar if the edges intersecting a common edge $a$ share a vertex $A$ on the same side of $a$. More precisely, orienting $e$ arbitrarily and the other edges towards $A$ results in a consistent orientation of the…

Computational Geometry · Computer Science 2021-08-31 Boris Klemz , Kristin Knorr , Meghana M. Reddy , Felix Schröder

A graph is $1$-planar, if it can be drawn in the plane such that there is at most one crossing on every edge. It is known, that $1$-planar graphs have at most $4n-8$ edges. We prove the following odd-even generalization. If a graph can be…

Combinatorics · Mathematics 2022-08-26 János Karl , Géza Tóth

A topological drawing of a graph is fan-planar if for each edge $e$ the edges crossing $e$ form a star and no endpoint of $e$ is enclosed by $e$ and its crossing edges. A fan-planar graph is a graph admitting such a drawing. Equivalently,…

Discrete Mathematics · Computer Science 2021-07-16 Michael Kaufmann , Torsten Ueckerdt

The concept of $k$-planarity is extensively studied in the context of Beyond Planarity. A graph is $k$-planar if it admits a drawing in the plane in which each edge is crossed at most $k$ times. The local crossing number of a graph is the…

Data Structures and Algorithms · Computer Science 2025-08-28 Tatsuya Gima , Yasuaki Kobayashi , Yuto Okada