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In this paper we introduce extensions and modifications of the classical degree sequence graphic realization problem studied by Erd\H{o}s-Gallai and Havel-Hakimi, as well as of the corresponding connected graphic realization version. We…

Discrete Mathematics · Computer Science 2015-09-24 Georgios Amanatidis , Bradley Green , Milena Mihail

In this document, we propose a bridge between the graphs and the geometric realizations of their Vietoris Rips complexes, i.e. Graphs, with their canonical \v{C}ech closure structure, have the same homotopy type that the realization of…

Algebraic Topology · Mathematics 2024-07-02 Jonathan Treviño-Marroquín

We describe a provably complete algorithm for the generation of a tight, possibly exact superset of all combinatorially distinct simple n-facet polytopes in R^d, along with their graphs, f-vectors, and face lattices. The technique applies…

Combinatorics · Mathematics 2009-08-13 Sandeep Koranne , Anand Kulkarni

In this note we present an infinite family of 2-connected graphs such that their matching polynomials have only integer zeros. This answers in negative a question of Akbari et al. [Graphs with integer matching polynomial zeros, Discrete…

Combinatorics · Mathematics 2021-09-14 Ebrahim Ghorbani

We characterise the form of all simple, finite graphs for which the girth of the graph is equal to the circumference of the graph. We apply this to prove a bound on the number of edges in such a graph.

Combinatorics · Mathematics 2022-10-11 Lewis Stanton , Jeffrey Thompson

We use the folding technique to show that generalized associahedra for non-simply-laced root systems (including non-crystallographic ones) can be obtained as sections of simply-laced generalized associahedra constructed by Bazier-Matte,…

Combinatorics · Mathematics 2024-01-17 Anna Felikson , Pavel Tumarkin , Emine Yildirim

Recent literature posed the problem of characterising the graph degree sequences with exactly one $3$-polytopal (i.e. planar, $3$-connected) realisation. This seems to be a difficult problem in full generality. In this paper, we…

Combinatorics · Mathematics 2025-08-05 Riccardo W. Maffucci

Laman graphs model planar frameworks that are rigid for a general choice of distances between the vertices. There are finitely many ways, up to isometries, to realize a Laman graph in the plane. Such realizations can be seen as solutions of…

Algebraic Geometry · Mathematics 2021-03-18 Jose Capco , Matteo Gallet , Georg Grasegger , Christoph Koutschan , Niels Lubbes , Josef Schicho

A minimally rigid graph, also called Laman graph, models a planar framework which is rigid for a general choice of distances between its vertices. In other words, there are finitely many ways, up to isometries, to realize such a graph in…

Computational Geometry · Computer Science 2022-01-04 Christoph Koutschan

We compute the canonical form of the cosmological polytope for any graph in terms of the dual of the shifted cosmological polytope in two different ways. On the way, we provide an explicit coordinate description of the dual of the…

Combinatorics · Mathematics 2026-03-05 Anna Birkemeyer , Torben Donzelmann , Mieke Fink , Martina Juhnke

We classify the finite connected-homogeneous digraphs, as well as the infinite such digraphs with precisely one end. This completes the classification of all the locally finite connected-homogeneous digraphs.

Combinatorics · Mathematics 2011-01-13 Matthias Hamann

Many applications, ranging from natural to social sciences, rely on graphlet analysis for the intuitive and meaningful characterization of networks employing micro-level structures as building blocks. However, it has not been thoroughly…

Social and Information Networks · Computer Science 2023-06-06 Colin Cleveland , Chin-Yen Lee , Shen-Fu Tsai , Wei-Hsuan Yu , Hsuan-Wei Lee

Let $S$ be a finite set of positive integers. A mixed hypergraph ${\cal H}$ is a one-realization of $S$ if its feasible set is $S$ and each entry of its chromatic spectrum is either 0 or 1. In [P. Zhao, K. Diao, Y. Chang and K. Wang, The…

Combinatorics · Mathematics 2013-06-05 Kefeng Diao , Vitaly I. Voloshin , Kaishun Wang , Ping Zhao

The degree partition of a simple graph is its degree sequence rearranged in weakly decreasing order. The polytope of degree partitions (respectively, degree sequences) is the convex hull of all degree partitions (respectively, degree…

Combinatorics · Mathematics 2007-05-23 Amitava Bhattacharya , S. Sivasubramanian , Murali K. Srinivasan

A sequence $\sigma$ of $p$ non-negative integers is unigraphic if it is the degree sequence of exactly one graph, up to isomorphism. A polyhedral graph is a $3$-connected, planar graph. We investigate which sequences are unigraphic with…

Combinatorics · Mathematics 2023-01-20 Jim Delitroz , Riccardo W. Maffucci

An isometric path between two vertices in a graph $G$ is a shortest path joining them. The isometric path number of $G$, denoted by $\ip(G)$, is the minimum number of isometric paths needed to cover all vertices of $G$. In this paper, we…

Combinatorics · Mathematics 2007-05-23 Jun-Jie Pan , Gerard J. Chang

Combinatorial Hopf algebras of trees exemplify the connections between operads and bialgebras. Painted trees were introduced recently as examples of how graded Hopf operads can bequeath Hopf structures upon compositions of coalgebras. We…

Combinatorics · Mathematics 2019-07-05 Lisa Berry , Stefan Forcey , Maria Ronco , Patrick Showers

In the recent years, several polynomial algorithms of a dynamical nature have been proposed to address the graph isomorphism problem. In this paper we propose a generalization of an approach exposed in cond-mat/0209112 and find that this…

Computational Complexity · Computer Science 2007-05-23 Marats Golovkins

Greb\'ik and Rocha [Fractional Isomorphism of Graphons, Combinatorica 42, pp 365-404 (2022)] extended the well studied notion of fractional isomorphism of graphs to graphons. We prove that fractionally isomorphic graphons can be…

Combinatorics · Mathematics 2023-09-22 Jan Hladký , Eng Keat Hng

Every generic linear functional $f$ on a convex polytope $P$ induces an orientation on the graph of $P$. From the resulting directed graph one can define a notion of $f$-arborescence and $f$-monotone path on $P$, as well as a natural graph…

Combinatorics · Mathematics 2021-04-26 Christos Athanasiadis , Jesús De Loera , Zhenyang Zhang