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In 2006 Qian [J. Qian, Degree complete graphs; Discrete Mathematics 306 (2006), 533--537] introduced the concept of degree complete graphs for labeled graphs. He also gave a characterization of these graphs in terms of two forbidden…

Combinatorics · Mathematics 2017-06-15 Sebastian Milz

An ortho-polygon visibility representation $\Gamma$ of a $1$-plane graph $G$ (OPVR of $G$) is an embedding preserving drawing that maps each vertex of $G$ to a distinct orthogonal polygon and each edge of $G$ to a vertical or horizontal…

Data Structures and Algorithms · Computer Science 2018-08-03 Giuseppe Liotta , Fabrizio Montecchiani , Alessandra Tappini

Given a hyperbolic surface, the set of all closed geodesics whose length is minimal form a graph on the surface, in fact a so-called fat graph, which we call the systolic graph. We study which fat graphs are systolic graphs for some surface…

Geometric Topology · Mathematics 2017-04-20 Bidyut Sanki , Siddhartha Gadgil

The identifiability problem arises naturally in a number of contexts in mathematics and computer science. Specific instances include local or global rigidity of graphs and unique completability of partially-filled tensors subject to rank…

Metric Geometry · Mathematics 2024-01-24 James Cruickshank , Fatemeh Mohammadi , Anthony Nixon , Shin-ichi Tanigawa

We explore pseudometrics for directed graphs in order to better understand their topological properties. The directed flag complex associated to a directed graph provides a useful bridge between network science and topology. Indeed, it has…

Algebraic Topology · Mathematics 2021-07-26 Ana Lucia Garcia-Pulido , Kathryn Hess , Jane Tan , Katharine Turner , Bei Wang , Naya Yerolemou

We introduce a characterization for split graphs by using edge contraction. Then, we use it to prove that any ($2K_{2}$, claw)-free graph with $\alpha(G) \geq 3$ is a split graph. Also, we apply it to characterize any pseudo-split graph.…

Combinatorics · Mathematics 2022-05-05 Hany Ibrahim

A celebrated theorem of Pippenger states that any almost regular hypergraph with small codegrees has an almost perfect matching. We show that one can find such an almost perfect matching which is `pseudorandom', meaning that, for instance,…

Combinatorics · Mathematics 2020-11-18 Stefan Ehard , Stefan Glock , Felix Joos

An intuitive property of a random graph is that its subgraphs should also appear randomly distributed. We consider graphs whose subgraph densities exactly match their expected values. We call graphs with this property for all subgraphs with…

Combinatorics · Mathematics 2020-03-10 Sebastian Jeon , Tanya Khovanova

The Divisibility Graph of a finite group $G$ has vertex set the set of conjugacy class lengths of non-central elements in $G$ and two vertices are connected by an edge if one divides the other. We determine the connected components of the…

Group Theory · Mathematics 2016-12-15 Adeleh Abdolghafourian , Mohammad A. Iranmanesh , Alice C. Niemeyer

This paper proposes a method for computing the visible occluding contours of subdivision surfaces. The paper first introduces new theory for contour visibility of smooth surfaces. Necessary and sufficient conditions are introduced for when…

Graphics · Computer Science 2022-06-09 Chenxi Liu , Pierre Bénard , Aaron Hertzmann , Shayan Hoshyari

A fundamental theorem in the study of Dunwoody manifolds is a classification of finite graphs on $2n$ vertices that satisfy seven conditions (concerning planarity, regularity, and a cyclic automorphism of order $n$). Its significance is…

Geometric Topology · Mathematics 2020-08-06 James Howie , Gerald Williams

A Graph is called 2-self-centered if its diameter and radius both equal to 2. In this paper, we begin characterizing these graphs by characterizing edge-maximal 2-self-centered graphs via their complements. Then we split characterizing…

Combinatorics · Mathematics 2019-10-29 Mohammad Hadi Shekarriz , Madjid Mirzavaziri , Kamyar Mirzavaziri

We describe the adjacency of vertices of the (unbounded version of the) set covering polyhedron, in a similar way to the description given by Chvatal for the stable set polytope. We find a sufficient condition for adjacency, and…

Combinatorics · Mathematics 2017-10-10 Néstor E. Aguilera , Ricardo D. Katz , Paola B. Tolomei

The extension complexity of a polytope measures its amenability to succinct representations via lifts. There are several versions of extension complexity, including linear, real semidefinite, and complex semidefinite. We focus on the last…

Combinatorics · Mathematics 2021-10-18 Tristram Bogart , João Gouveia , Juan Camilo Torres

An ortho-polygon visibility representation of an $n$-vertex embedded graph $G$ (OPVR of $G$) is an embedding-preserving drawing of $G$ that maps every vertex to a distinct orthogonal polygon and each edge to a vertical or horizontal…

Computational Geometry · Computer Science 2017-05-17 Emilio Di Giacomo , Walter Didimo , William S. Evans , Giuseppe Liotta , Henk Meijer , Fabrizio Montecchiani , Stephen K. Wismath

In this extended abstract, we present a PTAS for guarding the vertices of a weakly-visible polygon $P$ from a subset of its vertices, or in other words, a PTAS for computing a minimum dominating set of the visibility graph of the vertices…

Computational Geometry · Computer Science 2018-10-02 Matthew J. Katz

In this research, we investigate the subject of path-finding. A pruned version of visibility graph based on Candidate Vertices is formulated, followed by a new visibility check technique. Such combination enables us to quickly identify the…

Artificial Intelligence · Computer Science 2018-10-30 Pei Cao , Zhaoyan Fan , Robert X. Gao , Jiong Tang

In this paper, we characterize all unmixed d-uniform r-partite hypergraphs under a certain condition. Also we give a necessary condition for unmixedness in d-uniform hypergraphs with a perfect matching of size n. Finally we give a…

Commutative Algebra · Mathematics 2016-10-04 Reza Jafarpour-Golzari , Rashid Zaare-Nahandi

In this paper we consider the concept of preintersection numbers of a graph. These numbers are determined by the spectrum of the adjacency matrix of the graph, and generalize the intersection numbers of a distance-regular graph. By using…

Combinatorics · Mathematics 2016-04-20 A. Abiad , E. R. van Dam , M. A. Fiol

We prove a far-reaching strengthening of Szemer\'edi's regularity lemma for intersection graphs of pseudo-segments. It shows that the vertex set of such a graph can be partitioned into a bounded number of parts of roughly the same size such…

Combinatorics · Mathematics 2023-12-05 Jacob Fox , Janos Pach , Andrew Suk