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A bisection of a graph is a bipartition of its vertex set in which the number of vertices in the two parts differ by at most 1, and its size is the number of edges which go across the two parts. In this paper, motivated by several questions…

Combinatorics · Mathematics 2013-05-29 Choongbum Lee , Po-Shen Loh , Benny Sudakov

Spectral graph bisections are a popular heuristic aimed at approximating the solution of the NP-complete graph bisection problem. This technique, however, does not always provide a robust tool for graph partitioning. Using a special class…

Numerical Analysis · Mathematics 2015-12-22 John C. Urschel , Ludmil T. Zikatanov

This note provides a complete solution to a certain version of the edge-isoperimetric problem for powers of a cycle graph. Namely, it shows that the maximum number of edges inside a vertex subset of $C_n^s$ of size $k$ is achieved by a set…

Combinatorics · Mathematics 2026-01-13 Kristiyan Vasilev

In this paper we give upper bounds for the regularity of edge ideal of some classes of graphs in terms of invariants of graph. We introduce two numbers $a'(G)$ and $n(G)$ depending on graph $G$ and show that for a vertex decomposable graph…

Commutative Algebra · Mathematics 2016-01-05 Somayeh Moradi , Dariush Kiani

We give a formula for the v-number of a graded ideal that can be used to compute this number. Then we show that for the edge ideal $I(G)$ of a graph $G$ the induced matching number of $G$ is an upper bound for the v-number of $I(G)$ when…

Commutative Algebra · Mathematics 2021-10-15 Gonzalo Grisalde , Enrique Reyes , Rafael H. Villarreal

An obstacle representation of a graph $G$ is a set of points in the plane representing the vertices of $G$, together with a set of polygonal obstacles such that two vertices of $G$ are connected by an edge in $G$ if and only if the line…

Combinatorics · Mathematics 2017-07-18 Martin Balko , Josef Cibulka , Pavel Valtr

It was shown by Beisegel, Chudnovsky, Gurvich, Milani\v{c}, and Servatius in 2022 that every induced $2$-edge path in a vertex-transitive graph closes to an induced cycle. Similar results were obtained for 3-edge paths closing to cycles in…

Combinatorics · Mathematics 2025-10-08 Martin Milanič , Đorđe Mitrović

The problem of finding upper bounds for minimal vertex number of graphs with a given automorphism group is addressed in this article for the case of cyclic $2$-groups. We show that for any natural $n\ge 2$ there is an undirected graph…

Combinatorics · Mathematics 2015-04-06 Peteris Daugulis

Let $G$ be a relatively hyperbolic group that admits a decomposition into a finite graph of relatively hyperbolic groups structure with quasi-isometrically (qi) embedded condition. We prove that the set of conjugates of all the vertex and…

Group Theory · Mathematics 2019-12-06 Swathi Krishna

A connected digraph in which the in-degree of any vertex equals its out-degree is Eulerian; this baseline result is used as the basis of existence proofs for universal cycles (also known as ucycles or generalized deBruijn cycles or…

Combinatorics · Mathematics 2019-11-22 Amelia Cantwell , Juliann Geraci , Anant Godbole , Cristobal Padilla

An extremal graph for a graph $H$ on $n$ vertices is a graph on $n$ vertices with maximum number of edges that does not contain $H$ as a subgraph. Let $T_{n,r}$ be the Tur\'{a}n graph, which is the complete $r$-partite graph on $n$ vertices…

Combinatorics · Mathematics 2015-10-29 Xinmin Hou , Yu Qiu , Boyuan Liu

Finite obstruction sets for lower ideals in the minor order are guaranteed to exist by the Graph Minor Theorem. It has been known for several years that, in principle, obstruction sets can be mechanically computed for most natural lower…

Combinatorics · Mathematics 2016-09-06 Kevin Cattell , Michael J. Dinneen , Michael R. Fellows

We study how many comparability subgraphs are needed to partition the edge set of a perfect graph. We show that many classes of perfect graphs can be partitioned into (at most) two comparability subgraphs and this holds for almost all…

Combinatorics · Mathematics 2026-03-10 András Gyárfás , Márton Marits , Géza Tóth

We present lower and upper bounds for the geometric-arithmetic index of unicyclic graphs and provide extremal graphs for the corresponding bounds.

Combinatorics · Mathematics 2023-01-20 Sunyo Moon , Seungkook Park

Given an underlying undirected simple graph, we consider the set of all acyclic orientations of its edges. Each of these orientations induces a partial order on the vertices of our graph and, therefore, we can count the number of linear…

Combinatorics · Mathematics 2015-02-17 Benjamin Iriarte Giraldo

We study experiment design for unique identification of the causal graph of a simple SCM, where the graph may contain cycles. The presence of cycles in the structure introduces major challenges for experiment design as, unlike acyclic…

Machine Learning · Computer Science 2023-12-15 Ehsan Mokhtarian , Saber Salehkaleybar , AmirEmad Ghassami , Negar Kiyavash

We present progress on three old conjectures about longest paths and cycles in graphs. The first pair of conjectures, due to Lov\'{a}sz from 1969 and Thomassen from 1978, respectively, states that all connected vertex-transitive graphs…

Combinatorics · Mathematics 2025-10-29 Carla Groenland , Sean Longbrake , Raphael Steiner , Jérémie Turcotte , Liana Yepremyan

Let $G$ be a finite group. A number of graphs with the vertex set $G$ have been studied, including the power graph, enhanced power graph, and commuting graph. These graphs form a hierarchy under the inclusion of edge sets, and it is useful…

Combinatorics · Mathematics 2021-12-07 G. Arunkumar , Peter J. Cameron , Rajat Kanti Nath , Lavanya Selvaganesh

Given a graph, we associate each edge with the transposition which exchanges the endvertices. Fixing a linear order on the edge set, we obtain a permutation of the vertices. D\'enes proved that the permutation is a full cyclic permutation…

Combinatorics · Mathematics 2024-04-04 Shuhei Tsujie , Ryo Uchiumi

In the Minimum Clique Routing Problem on Cycles \textsc{MCRPC} we are given a cycle together with a set of demands (weighted origin-destination pairs) and the goal is to route all the pairs minimizing the maximum weighted clique of the…

Data Structures and Algorithms · Computer Science 2023-11-17 Mariana Escalante , Martín Matamala , Iván Rapaport , Paola Tolomei , Luis Miguel Torres
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