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Two cycles are {\em adjacent} if they have an edge in common. Suppose that $G$ is a planar graph, for any two adjacent cycles $C_{1}$ and $C_{2}$, we have $|C_{1}| + |C_{2}| \geq 11$, in particular, when $|C_{1}| = 5$, $|C_{2}| \geq 7$. We…

Combinatorics · Mathematics 2010-04-06 Tao Wang

Let X be a scroll over a rational surface. We construct a linear system of surfaces in P^3 yielding a birational map from P^3 to X. We apply this construction to the scrolls of Bordiga and Palatini.

Algebraic Geometry · Mathematics 2007-05-23 Emilia Mezzetti , Dario Portelli

Let $Oct_{1}^{+}$ and $Oct_{2}^{+}$ be the planar and non-planar graphs that obtained from the Octahedron by 3-splitting a vertex respectively. For $Oct_{1}^{+}$, we prove that a 4-connected graph is $Oct_{1}^{+}$-free if and only if it is…

Combinatorics · Mathematics 2021-02-16 Wenjian Jia , Shuai Kou , Chengfu Qin , Weihua Yang

The simple connected graphs may be classified by their cycle composition (number and lengths of cycles). This work derives the counting series of the simple connected graphs that have cycles of unrestricted number and length, but no…

Combinatorics · Mathematics 2018-08-21 Richard J. Mathar

For an elliptic curve $E$ defined over the field $\mathbb{C}$ of complex numbers, we classify all translates of elliptic curves in $E^3$ such that the $x$-coordinates satisfy a linear equation. This classification enables us to establish a…

Number Theory · Mathematics 2023-10-27 Jerson Caro , Natalia Garcia-Fritz

We show that for every l, there exists d_l such that every 3-edge-connected graph with minimum degree d_l can be edge-partitioned into paths of length l (provided that its number of edges is divisible by l). This improves a result asserting…

Combinatorics · Mathematics 2019-07-29 Tereza Klimošová , Stéphan Thomassé

This paper introduces a method for learning to generate line drawings from 3D models. Our architecture incorporates a differentiable module operating on geometric features of the 3D model, and an image-based module operating on view-based…

Computer Vision and Pattern Recognition · Computer Science 2020-04-07 Difan Liu , Mohamed Nabail , Aaron Hertzmann , Evangelos Kalogerakis

We announce results about flat (linkless) embeddings of graphs in 3-space. A piecewise-linear embedding of a graph in 3-space is called {\it flat} if every circuit of the graph bounds a disk disjoint from the rest of the graph. We have…

Combinatorics · Mathematics 2016-09-06 Neil Robertson , Paul Seymour , Robin Thomas

We study the question of polytopality of graphs: when is a given graph the graph of a polytope? We first review the known necessary conditions for a graph to be polytopal, and we provide several families of graphs which satisfy all these…

Metric Geometry · Mathematics 2013-04-30 Julian Pfeifle , Vincent Pilaud , Francisco Santos

In this article we investigate the structure of uniformly $k$-connected and uniformly $k$-edge-connected graphs. Whereas both types have previously been studied independent of each other, we analyze relations between these two classes. We…

Combinatorics · Mathematics 2021-03-08 Frank Göring , Tobias Hofmann , Manuel Streicher

A graph is said to be a segment graph if its vertices can be mapped to line segments in the plane such that two vertices have an edge between them if and only if their corresponding line segments intersect. Kratochv\'{i}l and Kub\v{e}na…

Combinatorics · Mathematics 2010-11-08 Mathew C. Francis , Jan Kratochvíl , Tomáš Vyskočil

A classic theorem by Steinitz states that a graph G is realizable by a convex polyhedron if and only if G is 3-connected planar. Zonohedra are an important subclass of convex polyhedra having the property that the faces of a zonohedron are…

Computational Geometry · Computer Science 2008-11-04 Muhammad Abdullah Adnan , Masud Hasan

For vertex and edge connectivity we construct infinitely many pairs of regular graphs with the same spectrum, but with different connectivity.

Combinatorics · Mathematics 2019-09-12 Willem H. Haemers

We construct minor-closed addable families of graphs that are subcritical and contain all planar graphs. This contradicts (one direction of) a well-known conjecture of Noy.

Combinatorics · Mathematics 2018-01-08 Agelos Georgakopoulos , Stephan Wagner

In this note we present a general approach to construct large digraphs from small ones. These are called expanded digraphs, and, as particular cases, we show the close relationship between lifted digraphs of voltage digraphs and line…

Combinatorics · Mathematics 2016-10-04 C. Dalfó , M. A. Fiol , M. Miller , J. Ryan

We present a simple mechanism, which can be randomised, for constructing sparse $3$-uniform hypergraphs with strong expansion properties. These hypergraphs are constructed using Cayley graphs over $\mathbb{Z}_2^t$ and have vertex degree…

Combinatorics · Mathematics 2019-06-26 David Conlon

We enumerate rooted 2-connected and 3-connected surface maps with respect to vertices and edges. We also derive the bivariate version of the large face-width result for random 3-connected maps. These results are then used to derive…

Combinatorics · Mathematics 2010-03-16 E. A. Bender , Z. Gao

Binary linear codes are constructed from graphs, in particular, by the generator matrix $[I_n|A]$ where $A$ is the adjacency matrix of a graph on $n$ vertices. A combinatorial interpretation of the minimum distance of such codes is given.…

Combinatorics · Mathematics 2021-01-08 Sudipta Mallik , Bahattin Yildiz

The Sierpi\'nski product of graphs generalises the vast and relevant class of Sierpi\'nski-type graphs, and is also related to the classic lexicographic product of graphs. Our first main results are necessary and sufficient conditions for…

Combinatorics · Mathematics 2025-06-23 Riccardo W. Maffucci

The game of cops and robbers is a pursuit game on graphs where a set of agents, called the cops try to get to the same position of another agent, called the robber. Cops and robbers has been studies on several classes of graphs including…

Combinatorics · Mathematics 2019-03-19 Seyyed Aliasghar Hosseini , Masood Masjoody , Ladislav Stacho