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A graph $G$ is a link-irregular graph if every two distinct vertices of $G$ have non-isomorphic links. The link of a vertex $v$ in $G$ is the subgraph induced by the neighbors of $v$ in $G$. Ali, Chartrand and Zhang [Discussiones…

Combinatorics · Mathematics 2025-06-13 Alexander Bastien , Omid Khormali

We investigate the computational complexity of finding temporally disjoint paths or walks in temporal graphs. There, the edge set changes over discrete time steps and a temporal path (resp. walk) uses edges that appear at monotonically…

Data Structures and Algorithms · Computer Science 2021-05-25 Nina Klobas , George B. Mertzios , Hendrik Molter , Rolf Niedermeier , Philipp Zschoche

A locally irregular multigraph is a multigraph whose adjacent vertices have distinct degrees. The locally irregular edge coloring is an edge coloring of a multigraph $G$ such that every color induces a locally irregular submultigraph of…

Combinatorics · Mathematics 2022-08-19 Igor Grzelec , Mariusz Woźniak

There has been extensive research on cycle lengths in graphs with large minimum degree. In this paper, we obtain several new and tight results in this area. Let $G$ be a graph with minimum degree at least $k+1$. We prove that if $G$ is…

Combinatorics · Mathematics 2015-09-01 Chun-Hung Liu , Jie Ma

We pursue the study of edge-irregulators of graphs, which were recently introduced in [Fioravantes et al. Parametrised Distance to Local Irregularity. IPEC, 2024]. That is, we are interested in the parameter Ie(G), which, for a given graph…

Combinatorics · Mathematics 2025-11-19 Julien Bensmail , Noémie Catherinot , Foivos Fioravantes , Clara Marcille , Nacim Oijid

We study a generalization of strongly regular graphs. We call a graph strongly walk-regular if there is an $\ell >1$ such that the number of walks of length $\ell$ from a vertex to another vertex depends only on whether the two vertices are…

Combinatorics · Mathematics 2013-01-31 Edwin R. van Dam , Gholamreza Omidi

Let $M\circ N$ denote the Schur product of two matrices $M$ and $N$. A graph $X$ with adjacency matrix $A$ is walk regular if $A^k\circ I$ is a constant times $I$ for each $k\ge0$, and $X$ is 1-walk-regular if it is walk regular and…

Combinatorics · Mathematics 2025-01-28 Chris Godsil , Wanting Sun , Xiaohong Zhang

Random walks on graphs are an essential primitive for many randomised algorithms and stochastic processes. It is natural to ask how much can be gained by running $k$ multiple random walks independently and in parallel. Although the cover…

Discrete Mathematics · Computer Science 2026-02-19 Nicolás Rivera , Thomas Sauerwald , John Sylvester

A graph $H$ is \emph{common} if the number of monochromatic copies of $H$ in a 2-edge-colouring of the complete graph $K_n$ is asymptotically minimised by the random colouring, or equivalently, $t_H(W)+t_H(1-W)\geq 2^{1-e(H)}$ holds for…

Combinatorics · Mathematics 2022-10-04 Jang Soo Kim , Joonkyung Lee

Distance-regular graphs are a key concept in Algebraic Combinatorics and have given rise to several generalizations, such as association schemes. Motivated by spectral and other algebraic characterizations of distance-regular graphs, we…

Combinatorics · Mathematics 2012-02-16 Cristina Dalfó , Edwin R. van Dam , Miquel Angel Fiol , Ernest Garriga , Bram L. Gorissen

Menger's well-known theorem from 1927 characterizes when it is possible to find $k$ vertex-disjoint paths between two sets of vertices in a graph $G$. Recently, Georgakopoulos and Papasoglu and, independently, Albrechtsen, Huynh, Jacobs,…

Combinatorics · Mathematics 2025-01-16 Tung Nguyen , Alex Scott , Paul Seymour

We say that a graph $G$ is $(2,m)$-linked if, for any distinct vertices $a_1,\ldots, a_m, b_1,b_2$ in $G$, there exist vertex disjoint connected subgraphs $A,B$ of $G$ such that $\{a_1, \ldots, a_m\}$ is contained in $A$ and $\{b_1,b_2\}$…

Combinatorics · Mathematics 2023-03-23 Xiying Du , Yanjia Li , Shijie Xie , Xingxing Yu

The concept of avoidable paths in graphs was introduced by Beisegel, Chudnovsky, Gurvich, Milani\v{c}, and Servatius in 2019 as a common generalization of avoidable vertices and simplicial paths. In 2020, Bonamy, Defrain, Hatzel, and…

Combinatorics · Mathematics 2025-04-18 Vladimir Gurvich , Matjaž Krnc , Martin Milanič , Mikhail Vyalyi

Let $F$ and $G$ be simple finite undirected graphs. A graph $G$ is called $F$-irregular if any two of its distinct vertices belong to different numbers of copies of $F$ in $G$. According to the strong conjecture about $F$-irregular graphs…

Combinatorics · Mathematics 2026-02-27 Tatiana Dovzhenok

Albertson has defined the irregularity of a simple undirected graph $G=(V,E)$ as $ \irr(G) = \sum_{uv\in E}|d_G(u)-d_G(v)|,$ where $d_G(u)$ denotes the degree of a vertex $u \in V$. Recently, this graph invariant gained interest in the…

Discrete Mathematics · Computer Science 2015-03-20 Hosam Abdo , Nathann Cohen , Darko Dimitrov

A vertex in a graph is simplicial if its neighborhood forms a clique. We consider three generalizations of the concept of simplicial vertices: avoidable vertices (also known as \textit{OCF}-vertices), simplicial paths, and their common…

Combinatorics · Mathematics 2019-07-30 Jesse Beisegel , Maria Chudnovsky , Vladimir Gurvich , Martin Milanič , Mary Servatius

Local Irregularity Conjecture states that every simple connected graph, except special cacti, can be decomposed into at most three locally irregular graphs, i.e., graphs in which adjacent vertices have different degrees. The connected…

Combinatorics · Mathematics 2025-02-13 Igor Grzelec , Alfréd Onderko , Mariusz Woźniak

Let $G = (V,E)$ be a graph, and for each $e \in E(G)$, let $L_e$ be a list of real numbers. Let $w:E(G) \to \cup_{e \in E(G)}L_e$ be an edge weighting function such that $w(e) \in L_e$ for each $e \in E(G)$, and let $c_w$ be the vertex…

Combinatorics · Mathematics 2014-01-28 Ben Seamone

An algorithm observes the trajectories of random walks over an unknown graph $G$, starting from the same vertex $x$, as well as the degrees along the trajectories. For all finite connected graphs, one can estimate the number of edges $m$ up…

Statistics Theory · Mathematics 2018-08-20 Anna Ben-Hamou , Roberto I. Oliveira , Yuval Peres

Menger's Edge Theorem asserts that there exist $k$ pairwise edge-disjoint paths between two vertices in an undirected graph if and only if a deletion of any $k-1$ or less edges does not disconnect these two vertices. Alternatively, there…

Combinatorics · Mathematics 2022-04-05 Avraham Goldstein