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We classify the Cohen-Macaulay binomial edge ideals of cactus and bicyclic graphs.

Commutative Algebra · Mathematics 2017-12-19 Giancarlo Rinaldo

The shrinking operation converts a hypergraph into a graph by choosing, from each hyperedge, two endvertices of a corresponding graph edge. A hypertree is a hypergraph which can be shrunk to a tree on the same vertex set. Klimo\v{s}ov\'{a}…

Combinatorics · Mathematics 2025-12-09 Karolína Hylasová , Tomáš Kaiser

This paper proposes a novel representation of decomposable graphs based on semi-latent tree-dependent bipartite graphs. The novel representation has two main benefits. First, it enables a form of sub-clustering within maximal cliques of the…

Methodology · Statistics 2017-12-05 Mohamad Elmasri

Lov\'{a}sz and Cherkassky discovered independently that, if $G$ is a finite graph and $T\subseteq V(G)$ such that the degree $d_G(v)$ is even for every vertex $v\in V(G)\setminus T$, then the maximum number of edge-disjoint paths which are…

Combinatorics · Mathematics 2023-07-21 Raphael W. Jacobs , Attila Joó , Paul Knappe , Jan Kurkofka , Ruben Melcher

An $s{\operatorname{-}}t$ minimum cut in a graph corresponds to a minimum weight subset of edges whose removal disconnects vertices $s$ and $t$. Finding such a cut is a classic problem that is dual to that of finding a maximum flow from $s$…

Quantum Physics · Physics 2024-02-06 Simon Apers , Arinta Auza , Troy Lee

This is a companion paper to the paper "Hyperstability in the Erdos-Sos Conjecture". In that paper the following rough structure theorem was proved for graphs G containing no copy of a bounded degree tree T: from any such G, one can delete…

Combinatorics · Mathematics 2024-09-24 Alexey Pokrovskiy

We call a finite undirected graph minimally k-matchable if it has at least k distinct perfect matchings but deleting any edge results in a graph which has not. An odd subdivision of some graph G is any graph obtained by replacing every edge…

Combinatorics · Mathematics 2016-08-05 Gasper Fijavz , Matthias Kriesell

Motivated by a conjecture of Gy\'arf\'as, recently B\"ottcher, Hladk\'y, Piguet, and Taraz showed that every collection $T_1,\dots,T_t$ of trees on $n$ vertices with $\sum_{i=1}^te(T_i)\leq \binom{n}{2}$ and with bounded maximum degree, can…

Combinatorics · Mathematics 2016-04-20 Silvia Messuti , Vojtěch Rödl , Mathias Schacht

For an integer $k\ge 2$, let $G$ be a graph with $m$ edges and without cycles of length $2k$. The pivotal Alon-Krivelevich-Sudakov Theorem on Max-Cuts states that $G$ has a bipartite subgraph with at least $m/2+\Omega(m^{(2k+1)/(2k+2)})$…

Combinatorics · Mathematics 2025-07-22 Jianfeng Hou , Siwei Lin , Qinghou Zeng

The edge-bandwidth of a graph is the minimum, over all labelings of the edges with distinct integers, of the maximum difference between labels of two incident edges. We prove that edge-bandwidth is at least as large as bandwidth for every…

Combinatorics · Mathematics 2007-05-23 Tao Jiang , Dhruv Mubayi , Aditya Shastri , Douglas B. West

The minimum cut problem for an undirected edge-weighted graph asks us to divide its set of nodes into two blocks while minimizing the weight sum of the cut edges. In this paper, we engineer the fastest known exact algorithm for the problem.…

Data Structures and Algorithms · Computer Science 2018-08-17 Monika Henzinger , Alexander Noe , Christian Schulz

Minimum Bisection denotes the NP-hard problem to partition the vertex set of a graph into two sets of equal sizes while minimizing the width of the bisection, which is defined as the number of edges between these two sets. We first consider…

Combinatorics · Mathematics 2017-08-23 Cristina G. Fernandes , Tina Janne Schmidt , Anusch Taraz

In this article, we characterize all unmixed and Cohen-Macaulay parity binomial edge ideals of cactus and chordal graphs in terms of the structural properties of the graph.

Commutative Algebra · Mathematics 2026-03-18 Deblina Dey , A. V. Jayanthan , Sarang Sane

Hoffmann-Ostenhof's Conjecture states that states that the edge set of every connected cubic graph can be decomposed into a spanning tree, a matching and a $2$-regular subgraph. In this paper, we show that the conjecture holds for claw-free…

Combinatorics · Mathematics 2018-10-02 Milad Ahanjideh , Elham Aboomahigir

In this paper, our goal is to characterize two graph classes based on the properties of minimal vertex (edge) separators. We first present a structural characterization of graphs in which every minimal vertex separator is a stable set. We…

Discrete Mathematics · Computer Science 2011-03-16 Mrinal Kumar , Gaurav Maheswari , N. Sadagopan

In this paper we continue a long line of work on representing the cut structure of graphs. We classify the types minimum vertex cuts, and the possible relationships between multiple minimum vertex cuts. As a consequence of these…

Data Structures and Algorithms · Computer Science 2021-02-16 Seth Pettie , Longhui Yin

We design succinct encodings of {\it series-parallel, block-cactus} and {\it 3-leaf power} graphs while supporting the basic navigational queries such as degree, adjacency and neighborhood {\it optimally} in the RAM model with logarithmic…

Data Structures and Algorithms · Computer Science 2021-08-27 Sankardeep Chakraborty , Seungbum Jo , Kunihiko Sadakane , Srinivasa Rao Satti

A bound on consecutive clique numbers of graphs is established. This bound is evaluated and shown to often be much better than the bound of the Kruskal-Katona theorem. A bound on non-consecutive clique numbers is also proven.

Combinatorics · Mathematics 2007-10-23 Andy Frohmader

Treewidth is a graph parameter that plays a fundamental role in several structural and algorithmic results. We study the problem of decomposing a given graph $G$ into node-disjoint subgraphs, where each subgraph has sufficiently large…

Data Structures and Algorithms · Computer Science 2013-04-08 Chandra Chekuri , Julia Chuzhoy

We present a deterministic near-linear time algorithm that computes the edge-connectivity and finds a minimum cut for a simple undirected unweighted graph G with n vertices and m edges. This is the first o(mn) time deterministic algorithm…

Data Structures and Algorithms · Computer Science 2018-10-30 Ken-ichi Kawarabayashi , Mikkel Thorup