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The maximum genus $\gamma_M(G)$ of a graph G is the largest genus of an orientable surface into which G has a cellular embedding. Combinatorially, it coincides with the maximum number of disjoint pairs of adjacent edges of G whose removal…

Combinatorics · Mathematics 2015-01-30 Michal Kotrbcik , Martin Skoviera

Given a multigraph $G$, the all-terminal reliability $R(G,p)$ is the probability that $G$ remains connected under percolation with parameter $p$. Fixing the number of vertices $n$ and edges $m$, we investigate which graphs maximize $R(G,p)$…

Combinatorics · Mathematics 2024-11-26 Lorents F. Landgren , Jeffrey E. Steif

In this paper, we make progress on a question related to one of Galvin that has attracted substantial attention recently. The question is that of determining among all graphs $G$ with $n$ vertices and $\Delta(G)\leq r$, which has the most…

Combinatorics · Mathematics 2014-05-07 Jonathan Cutler , A. J. Radcliffe

A graph construction that produces a k-regular graph on n vertices for any choice of k >= 3 and n = m(k+1) for integer m >= 2 is described. The number of Hamiltonian cycles in such graphs can be explicitly determined as a function of n and…

Combinatorics · Mathematics 2016-08-03 Michael Haythorpe

The maximum likelihood threshold (MLT) of a graph $G$ is the minimum number of samples to almost surely guarantee existence of the maximum likelihood estimate in the corresponding Gaussian graphical model. Recently a new characterization of…

We find the maximum number of maximal independent sets in two families of graphs: all graphs with $n$ vertices and at most $r$ cycles, and all such graphs that are also connected. In addition, we characterize the extremal graphs.

Combinatorics · Mathematics 2007-05-23 Chee Ying Goh , Khee Meng Koh , Bruce E. Sagan , V. Vatter

Matroid is a generalization of many fundamental objects in combinatorial mathematics , and matroid intersection problem is a classical subject in combinatorial optimization . However , only the intersection of two matroids are well…

Combinatorics · Mathematics 2023-01-10 Tianyu Liu

We introduce the cycle intersection graph of a graph, an adaptation of the cycle graph of a graph, and use the structure of these graphs to prove an upper bound for the decycling number of all even graphs. This bound is shown to be…

Combinatorics · Mathematics 2018-10-11 Michael Cary

The study of the existence of hamiltonian cycles in a graph is a classic problem in graph theory. By incorporating toughness and spectral conditions, we can consider Chv\'{a}tal's conjecture from another perspective: what is the spectral…

Combinatorics · Mathematics 2022-04-06 Dandan Fan , Huiqiu Lin , Hongliang Lu

The spread of a real symmetric matrix is defined as the difference between its largest and smallest eigenvalue. The study of graph-related matrices has attracted considerable attention, leading to a substantial body of findings. In this…

Combinatorics · Mathematics 2025-09-04 Lele Liu , Yi-Zheng Fan , Yi Wang , Wenyan Wang

We explore the rigidity of generic frameworks in 3-dimensions whose underlying graph is close to being planar. Specifically we consider apex graphs, edge-apex graphs and their variants and prove independence results in the generic…

Combinatorics · Mathematics 2024-02-28 Sean Dewar , Georg Grasegger , Eleftherios Kastis , Anthony Nixon , Brigitte Servatius

We give new characterizations for the class of uniformly dense matroids and study applications of these characterizations to graphic and real representable matroids. We show that a matroid is uniformly dense if and only if its base polytope…

Combinatorics · Mathematics 2026-02-03 Karel Devriendt , Raffaella Mulas

Let $G$ be a simple connected graph, and $D(G)$ be the distance matrix of $G$. Suppose that $D_{\max}(G)$ and $\lambda_1(G)$ are the maximum row sum and the spectral radius of $D(G)$, respectively. In this paper, we give a lower bound for…

Combinatorics · Mathematics 2020-09-04 Lele Liu , Haiying Shan , Changxiang He

In the 1960s, Erd\H{o}s and his cooperators initiated the research of the maximum numbers of edges in a graph or a planar graph on $n$ vertices without $k$ edge-disjoint cycles. This problem had been solved for $k\leq4$. As pointed out by…

Combinatorics · Mathematics 2022-07-21 Zhai Mingqing , Liu Muhuo

Let $\mathcal{F}$ denote a set of graphs. A graph $G$ is said to be $\mathcal{F}$-free if it does not contain any element of $\mathcal{F}$ as a subgraph. The Tur\'an number is the maximum possible number of edges in an $\mathcal{F}$-free…

Combinatorics · Mathematics 2023-02-01 Shuchao Li , Wanting Sun , Wei Wei

Let $G$ be a simple graph with $2n$ vertices and a perfect matching. We denote by $f(G)$ and $F(G)$ the minimum and maximum forcing number of $G$, respectively. Hetyei obtained that the maximum number of edges of graphs $G$ with a unique…

Combinatorics · Mathematics 2022-11-23 Qianqian Liu , Heping Zhang

Let $G$ be a simple graph with a perfect matching. Deng and Zhang showed that the maximum anti-forcing number of $G$ is no more than the cyclomatic number. In this paper, we get a novel upper bound on the maximum anti-forcing number of $G$…

Combinatorics · Mathematics 2023-06-22 Lingjuan Shi , Heping Zhang

The main purpose of this paper is to prove the uniqueness of a graph attaining the maximum of the number of independent sets over all $k$-regular graphs on $n$ vertices for $2k|n$.

Combinatorics · Mathematics 2016-03-01 Alexei Dmitriev , Alex Dainiak

This article provides sharp bounds for the maximum number of edges possible in a simple graph with restricted values of two of the three parameters, namely, maxi- mum matching size, independence number and maximum degree. We also construct…

Combinatorics · Mathematics 2012-03-08 Niraj Khare , Nishali Mehta , Naushad Puliyambalath

For a graph G with real weights assigned to the vertices (edges), the MAX H-SUBGRAPH problem is to find an H-subgraph of G with maximum total weight, if one exists. The all-pairs MAX H-SUBGRAPH problem is to find for every pair of vertices…

Data Structures and Algorithms · Computer Science 2007-05-23 Virginia Vassilevska , Ryan Williams , Raphael Yuster