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A graph G on n vertices is said to be extendable if G can be modified to form a new graph H on more than n vertices, while preserving the degrees of the vertices common to G and H. The added vertices all have the same degree and we define…

Combinatorics · Mathematics 2018-03-09 Ghurumuruhan Ganesan

Graph neural networks (GNNs) are typically applied to static graphs that are assumed to be known upfront. This static input structure is often informed purely by insight of the machine learning practitioner, and might not be optimal for the…

We show that there are $O(n \cdot 4^{n/11})$ planar graphs on $n$ vertices which do not admit a simultaneous straight-line embedding on any $n$-point set in the plane. In particular, this improves the best known bound $O(n!)$ significantly.

Combinatorics · Mathematics 2023-10-26 Ritesh Goenka , Pardis Semnani , Chi Hoi Yip

We introduce and study the problem of constructing geometric graphs that have few vertices and edges and that are universal for planar graphs or for some sub-class of planar graphs; a geometric graph is \emph{universal} for a class…

Combinatorics · Mathematics 2020-06-22 Fabrizio Frati , Michael Hoffmann , Csaba D. Tóth

Let P_{n,m} denote the graph taken uniformly at random from the set of all planar graphs on {1,2,..., n} with exactly m(n) edges. We use counting arguments to investigate the probability that P_{n,m} will contain given components and…

Combinatorics · Mathematics 2011-01-27 Chris Dowden

We discuss the problem of embedding graphs in the plane with restrictions on the vertex mapping. In particular, we introduce a technique for drawing planar graphs with a fixed vertex mapping that bounds the number of times edges bend. An…

Computational Geometry · Computer Science 2012-06-05 Taylor Gordon

A set $\mathcal{G}$ of planar graphs on the same number $n$ of vertices is called simultaneously embeddable if there exists a set $P$ of $n$ points in the plane such that every graph $G \in \mathcal{G}$ admits a (crossing-free)…

Combinatorics · Mathematics 2023-09-14 Raphael Steiner

In this article we study an asymptotic expansion for $C_n$, the number of connected chord diagrams on $n$ chords. The expansion is obtained in earlier work by means of alien derivatives applied to the generating series of connected chord…

Combinatorics · Mathematics 2021-07-06 Ali Assem Mahmoud , Karen Yeats

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

Counting linear extensions is a fundamental problem in poset theory. It is known to be #P-complete, with polynomial-time formulas available in special cases. In this work, we develop new recursive formulas for counting linear extensions of…

Combinatorics · Mathematics 2026-01-22 Daniela Egas Santander , Matteo Santoro , Jason P. Smith

We consider embeddings of maximal outerplanar graphs whose vertices all lie on a cycle $\mathcal{C}$ bounding a face. Each edge of the graph that is not in $\mathcal{C}$, a chord, is assigned a length equal to the length of the shortest…

Combinatorics · Mathematics 2024-04-18 Haley Broadus , Elena Pavelescu

We give an efficient construction of a reasonably small dominating set in a circulant graph on $n$ notes and $k$ distinct chord lengths. This result is based on bounds on some double exponential sums. .

Combinatorics · Mathematics 2016-03-03 Igor E. Shparlinski

A chord diagram refers to a set of chords with distinct endpoints on a circle. The intersection graph of a chord diagram $\cal C$ is defined by substituting the chords of $\cal C$ with vertices and by adding edges between two vertices…

Combinatorics · Mathematics 2015-01-08 Huseyin Acan

A dominating set of a graph is a set of vertices such that every vertex not in the set has at least one neighbor in the set. The problem of counting dominating sets is #P-complete for chordal graphs but solvable in polynomial time for its…

Discrete Mathematics · Computer Science 2022-07-04 Min-Sheng Lin

A graph is \emph{fan-crossing free} if it has a drawing in the plane so that each edge is crossed by independent edges, that is the crossing edges have distinct vertices. On the other hand, it is \emph{fan-crossing} if the crossing edges…

Discrete Mathematics · Computer Science 2020-12-14 Franz J. Brandenburg

A special case of a combinatorial theorem of De Bruijn and Erdos asserts that every noncollinear set of n points in the plane determines at least n distinct lines. Chen and Chvatal suggested a possible generalization of this assertion in…

A curve $\gamma$ that connects $s$ and $t$ has the increasing chord property if $|bc| \leq |ad|$ whenever $a,b,c,d$ lie in that order on $\gamma$. For planar curves, the length of such a curve is known to be at most $2\pi/3 \cdot |st|$.…

Computational Geometry · Computer Science 2025-09-03 Adrian Dumitrescu , Zsolt Lángi

A conjecture regarding the structure of expander graphs is discussed.

Combinatorics · Mathematics 2020-10-20 Itai Benjamini , Mikolaj Fraczyk

We study noncrossing geometric graphs and their disjoint compatible geometric matchings. Given a cycle (a polygon) P we want to draw a set of pairwise disjoint straight-line edges with endpoints on the vertices of P such that these new…

Combinatorics · Mathematics 2020-08-20 Alexander Pilz , Jonathan Rollin , Lena Schlipf , André Schulz

Strongly chordal graphs are a subclass of chordal graphs. The interest in this subclass stems from the fact that many problems which are NP-complete for chordal graphs are solvable in polynomial time for this subclass. However, we are not…

Data Structures and Algorithms · Computer Science 2018-04-25 Md. Zamilur Rahman , Asish Mukhopadhyay , Yash P. Aneja