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This paper provides a friendly introduction to chip-firing games and graph gonality. We use graphs coming from the five Platonic solids to illustrate different tools and techniques for studying these games, including independent sets,…

Algebraic Geometry · Mathematics 2024-07-09 Marchelle Beougher , Kexin Ding , Max Everett , Robin Huang , Chan Lee , Ralph Morrison , Ben Weber

A simple graph is called triangular if every edge of it belongs to a triangle. We conjecture that any graphical degree sequence all terms of which are greater than or equal to 4 has a triangular realisation, and establish this conjecture…

Combinatorics · Mathematics 2023-04-03 Benjamin Egan , Yuri Nikolayevsky

Partial duality generalizes the fundamental concept of the geometric dual of an embedded graph. A partial dual is obtained by forming the geometric dual with respect to only a subset of edges. While geometric duality preserves the genus of…

Combinatorics · Mathematics 2013-11-18 Iain Moffatt

The gonality sequence $(d_r)_{r\geq1}$ of a smooth algebraic curve comprises the minimal degrees $d_r$ of linear systems of rank $r$. We explain two approaches to compute the gonality sequence of smooth curves in $\mathbb{P}^1 \times…

Algebraic Geometry · Mathematics 2017-09-22 Filip Cools , Michele D'Adderio , David Jensen , Marta Panizzut

We prove that the (divisorial) gonality of a finite connected graph is lower bounded by its treewidth. We show that equality holds for grid graphs and complete multipartite graphs. We prove that the treewidth lower bound also holds for…

Combinatorics · Mathematics 2022-01-04 Josse van Dobben de Bruyn , Dion Gijswijt

We study chip-firing games on multigraphs whose underlying simple graphs are trees, paths, and stars, denoted as banana trees, paths, and stars respectively. We present a polynomial time algorithm to compute the divisorial gonality of…

Divisorial gonality and stable divisorial gonality are graph parameters, which have an origin in algebraic geometry. Divisorial gonality of a connected graph $G$ can be defined with help of a chip firing game on $G$. The stable divisorial…

Computational Complexity · Computer Science 2018-08-22 Hans L. Bodlaender , Marieke van der Wegen , Tom C. van der Zanden

Clustering algorithms for large networks typically use modularity values to test which partitions of the vertex set better represent structure in the data. The modularity of a graph is the maximum modularity of a partition. We consider the…

Combinatorics · Mathematics 2022-12-22 Colin McDiarmid , Fiona Skerman

For a given number of colors, $s$, the guessing number of a graph is the (base $s$) logarithm of the cardinality of the largest family of colorings of the vertex set of the graph such that the color of each vertex can be determined from the…

Combinatorics · Mathematics 2020-09-11 Jo Martin , Puck Rombach

Recently, a new set of multigraph parameters was defined, called "gonalities". Gonality bears some similarity to treewidth, and is a relevant graph parameter for problems in number theory and multigraph algorithms. Multigraphs of gonality 1…

Data Structures and Algorithms · Computer Science 2019-09-24 Jelco M. Bodewes , Hans L. Bodlaender , Gunther Cornelissen , Marieke van der Wegen

In [1] the problem of finding a sharp lower bound on lower against number of a general graph is mentioned as an open question. We solve the problem by establishing a tight lower bound on lower against number of a general graph in terms of…

Combinatorics · Mathematics 2019-08-27 Babak Samadi

Let G be a simple graph without isolated vertices. For a vertex i in G, the degree d_i is the number of vertices adjacent to i and the average 2-degree m_i is the mean of the degrees of the vertices which are adjacent to i. The sequence of…

Combinatorics · Mathematics 2018-11-08 Yu-pei Huang , Chia-an Liu , Chih-wen Weng

For any smooth irreducible projective curve $X$, the gonality sequence $\{d_r \;| \; r \in \mathbb N \}$ is a strictly increasing sequence of positive integer invariants of $X$. In most known cases $d_{r+1}$ is not much bigger than $d_r$.…

Algebraic Geometry · Mathematics 2010-07-16 H. Lange , G. Martens

We investigate the tree gonality of a genus-$g$ metric graph, defined as the minimum degree of a tropical morphism from any tropical modification of the metric graph to a metric tree. We give a combinatorial constructive proof that this…

Combinatorics · Mathematics 2020-07-31 Jan Draisma , Alejandro Vargas

Let $G$ be a finite group, and let ${\rm{cd}}(G)$ denote the set of degrees of the irreducible complex characters of $G$. The degree graph $\Delta(G)$ of $G$ is defined as the simple undirected graph whose vertex set ${\rm{V}}(G)$ consists…

Group Theory · Mathematics 2018-11-06 Zeinab Akhlaghi , Silvio Dolfi , Emanuele Pacifici , Lucia Sanus

A graph generative model defines a distribution over graphs. One type of generative model is constructed by autoregressive neural networks, which sequentially add nodes and edges to generate a graph. However, the likelihood of a graph under…

Machine Learning · Statistics 2021-06-15 Xiaohui Chen , Xu Han , Jiajing Hu , Francisco J. R. Ruiz , Liping Liu

We examine connections between the gonality, treewidth, and orientable genus of a graph. Especially, we find that hyperelliptic graphs in the sense of Baker and Norine are planar. We give a notion of a bielliptic graph and show that each of…

Number Theory · Mathematics 2017-04-21 James Stankewicz

In this paper, we introduce the concept of curling subsequence of simple, finite and connected graphs. A curling subsequence is a maximal subsequence $C$ of the degree sequence of a simple connected graph $G$ for which the curling number…

Combinatorics · Mathematics 2015-07-08 Johan Kok , Naduvath Sudev , Chithra Sudev

Graph burning is a graph process that models the spread of social contagion. Initially, all the vertices of a graph $G$ are unburnt. At each step, an unburnt vertex is put on fire and the fire from burnt vertices of the previous step…

Combinatorics · Mathematics 2023-11-15 Sandip Das , Sk Samim Islam , Ritam M Mitra , Sanchita Paul

A graph $G$ of order $2n$ is called degree-equipartite if for every $n$-element set $A\subseteq V(G)$, the degree sequences of the induced subgraphs $G[A]$ and $G[V(G)\setminus A]$ are the same. In this paper, we characterize all…

Combinatorics · Mathematics 2011-08-09 Khodakhast Bibak , Mohammad Hassan Shirdareh Haghighi