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2 votes
1 answer
127 views

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 ...
Xin Zhang's user avatar
  • 1,190
1 vote
1 answer
75 views

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 $G$ ...
Hao S's user avatar
  • 111
5 votes
2 answers
474 views

Another graph characteristic

This question concerns a method of drawing graphs and a graph characteristic about which I want to learn more. Consider a connected directed graph with at least one node with in-degree 0 and one node ...
Hans-Peter Stricker's user avatar
10 votes
2 answers
724 views

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 ...
Joseph O'Rourke's user avatar
13 votes
1 answer
933 views

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}{...
Jan Kyncl's user avatar
  • 6,101
3 votes
1 answer
1k views

Graph drawing: unrooted undirected tree graphs with specified edge lengths

Has Joseph Felsenstein's equal daylight layout been analyzed by the graph drawing community? The following description is taken from his drawtree documentation (Wayback Machine): "This ...
psd's user avatar
  • 266