All Questions
Tagged with graph-drawing co.combinatorics
29 questions
1
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98
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Is there any known upper bound for the local crossing number of a graph drawing in the plane?
The local crossing number ${\rm LCR(G)}$ of a graph $G$ is defined as the least nonnegative integer $k$ such that the graph has a $k$-planar drawing. In other words, it is the smallest possible number ...
- 1,190
1
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1
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115
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Bounds on lengths of boxes in bounded-degree box graphs
$\DeclareMathOperator{\box}{\operatorname{box}}$$\DeclareMathOperator{\cub}{\operatorname{cub}}$
This is a follow up and an extension of another question I asked recently.
A box graph is a graph ...
- 277
1
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1
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194
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Bounds on lengths of intervals in bounded-degree interval graphs
A graph is said to be an interval graph if its vertices can be associated with (closed) intervals on the real line $\mathbb R$ and there is an edge between two vertices if and only if the ...
- 277
1
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0
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42
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What lower bounds are known for pair crossing number and related questions in multigraphs?
So in terms of crossing number https://arxiv.org/pdf/1808.10480 gives a lower bound of $O(e^{2.5}/n^{1.5})$ for multigraphs with no face of length 2 with no node contained inside.
What do we know ...
- 111
1
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173
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Who introduced the concept of beyond planar graphs?
The concept of planar graphs seems to be standard (I'm also not sure who first used this term), and recently, beyond planar graphs attract a lot of interest in the field of graph drawing. I know that ...
- 1,851
6
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3
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526
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Enumerating all inequivalent planar embeddings of a planar graph
Graph $G$ can be embedded (or has an embedding) in the space if $G$ can be drawn in the space if $G$ can be drawn in such a way that no two edges cross except at an end-vertex in common. A Graph $G$ ...
- 1,851
3
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0
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136
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Is there a more intuitive proof that a 1-planar graph with minimum degree 7 contains a $K_4$?
In the following paper, Hudák Dávid, and Tomáš Madaras give the following Theorem 1.1.
Hudák, Dávid, and Tomáš Madaras. "On local properties of 1-planar graphs with high minimum degree." ...
- 1,851
20
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3
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1k
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Can a 3-regular non-1-planar graph be constructed?
A $1$-planar graph is a graph which has a drawing on the plane such that each edge has at most one crossing.
I used nauty to generate all 3-regular graphs up to ...
- 1,851
7
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0
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155
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Why is the crossing number of Tutte 12-cage 170?
From the Wikipedia entry on Tutte 12-cage , it is stated that the crossing number of Tutte 12-cage is 170, but the cited references do not seem to provide sufficient explanation for this.
Exoo, G. &...
- 1,851
4
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1
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214
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Find all 2-planar drawings of $K_6$ and $K_7$
A $k$-planar graph is a graph which can be embedded with at most $k$ crossings per
edge.
It is proved that a complete graph $K_n$ is 2-planar if and only if $n\le 7$.
Angelini P., Bekos M. A., ...
- 1,851
9
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3
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470
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Is it possible that every edge in a 1-planar drawing with minimum number of crossings is crossed?
A graph is 1-planar is it has drawing in the plane so that each edge is crossed at most once. Here we also assume the drawing satisfies (1) no edge is self-crossed; (2) no two adjacent edges are ...
- 557
5
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1
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220
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Is the crossing number of the line graph of $K_5$ determined?
The line graph of an undirected graph $G$ is another graph $L(G)$ that represents the adjacencies between edges of $G$. $L(G)$ is constructed in the following way: for each edge in $G$, make a vertex ...
- 1,851
8
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1
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527
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Find all Non-isomorphic good drawings of $K_{3,3}$？
Sometimes I look at all non-isomorphic good drawings of graphs on a plane or sphere.
Good drawing means that no edge crosses itself, no two edges cross more than once, and no two edges incident with ...
- 1,851
2
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1
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127
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The density of a tripartite 1-planar graph
1-planar graphs are those can be drawn in the plane so that there is at most one crossing per edge. We know that the maximum number of edges of an $n$-vertex 1-planar graph is at most $4n-8$, and the ...
- 1,190
4
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131
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What is the crossing number of dodecahedron with a copy of $K_5$ inside each face
Suppose we are given a regular dodecahedron. Then we add five crossed edges inside each of its faces (actually, inside each face it is a copy of $K_5$). It is clear that this drawing has 60 crossings. ...
- 1,190
5
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1
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263
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What is the crossing number of cube with a pair of crossing edges inside each face
Suppose we are given a cube and we add a pair of crossing edges inside each of its faces. It is clear that this drawing has 6 crossings. My question is whether such a graph has crossing number 6? How ...
- 1,190
5
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2
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251
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Finding a special plane graph with some requirements on the faces
Is there a plane graph such that
(1) the outer face has degree 3, i.e, is a triangle,
(2) every inner face has degree 5, and
(3) any two degree 5 faces share at most one commong edge.
- 1,190
3
votes
1
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200
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Looking for examples showing that the crossing number may not be realized by the drawings with local crossing number
The crossing number $cr(G)$ of a graph $G$ is the lowest number of edge crossings of a plane drawing of the graph $G$. The local crossing number of a drawing of a graph is the largest number of ...
- 1,190
7
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2
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252
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There is a 3-connected 5-regular simple $n$-vertex planar graph iff $n$ satisfies....?
Is there any characterization on the set of integers $n$ such that there is a 3-connected 5-regular simple $n$-vertex planar graph?
- 1,190
6
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2
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293
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Is there any maximal 1-planar or 2-planar graph that is not 3-connected
A graph is $k$-planar if it can be drawn in the plane so that each edge is crossed at most $k$ times. A $k$-planar graph $G$ is maximal if $G+uv$ is not $k$-planar for any non-adjacent vertices $u,v\...
- 1,190
1
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75
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Given a vertex $u$ (of bounded degree $k$) and another vertex $v$ in a planar graph, what is the smallest number of "curves"?
Given a vertex $u$ (of bounded degree $k$) and another vertex $v$ in a planar graph $G$, what is the smallest number of "curves" in the plane drawn from $u$ to $v$ such that no $u$--$v$ path in $G$ ...
- 111
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2
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553
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"Locally Nonplanar" graph
A 2-connected $3$-connected graph $G$ is "Almost Planar" Locally Nonplanar if it has a a $2$-connected spanning subgraph $H$ and an embedding in the plane such that $H$ is planar in this embedding and ...
- 1,034
5
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1
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479
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Can all crossings in a graph be moved to one point?
Consider a graph $G$ with at least two unavoidable crossings, say, the disjoint union of two copies of $K_5$. Can such a graph always be drawn so that there is only one singular point (where all ...
- 4,829
5
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0
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230
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Minimal algebraic degree of symmetric unit distance embedding of Heawood graph
I'm looking at embeddings of the Heawood graph in the plane as unit distance graph. Apparently the first such embedding was given by Gerbracht, 2009 and has algebraic (over the rationals) coordinates ...
- 10.7k
12
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3
answers
1k
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Is every graph an edge-crossing graph?
Consider a circular drawing of a simple (in particular, loopless) graph $G$ in which edges are drawn as straight lines inside the circle. The crossing graph for such a drawing is the simple graph ...
- 195
10
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2
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724
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Bounds on chromatic number of $k$-planar graphs
A $1$-planar graph can be drawn in the
plane so that each arc is crossed at most once by another arc.
A $k$-planar graph can be drawn so that each arc is crossed at most $k$ times.
Planar graphs are ...
- 151k
1
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1
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228
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Counting edges in embeddable CW-complexes in R^3
Using Euler's formula ($V-E+F = 2$ where $V$, $E$ and $F$ are the number of vertices, edges and faces), we can easily count the number of edges in maximal graphs that are embeddable in plane: 3n-6. I ...
- 415
13
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1
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933
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Drawings of complete graphs with $Z(n)$ crossings
Hill conjectured that the minimum number of crossings in a drawing of the complete graph $K_n$ in the plane is exactly
$$Z(n) = \frac{1}{4} \bigg\lfloor\frac{n}{2}\bigg\rfloor \left\lfloor\frac{n-1}{...
- 6,101
7
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2
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1k
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Planar layouts of bipartite graphs
Instances of SAT induce a bipartite graph between clauses vertices and variable vertices, and for planar 3SAT, the resulting bipartite graph is planar.
It would be very convenient if there was a ...
- 4,462