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Let $G$ be a connected graph with $n$ vertices. The resistance distance $\Omega_{G}(i,j)$ between any two vertices $i$ and $j$ of $G$ is defined as the effective resistance between them in the electrical network constructed from $G$ by…

Combinatorics · Mathematics 2026-03-27 Wensheng Sun , Yujun Yang , Shou-Jun Xu

A middle-cube is an induced subgraph consisting of nodes at the middle two layers of a hypercube. The middle-cubes are related to the well-known Revolving Door (Middle Levels) conjecture. We study the middle-cube graph by completely…

Combinatorics · Mathematics 2009-11-03 Ke Qiu , Rong Qiu , Yong Jiang , Jian Shen

The circumference of a graph is the length of its longest cycles. Jackson established a conjecture of Bondy by showing that the circumference of a 3-connected cubic graph of order $n$ is $\Omega(n^{0.694})$. Bilinski {\it et al.} improved…

Combinatorics · Mathematics 2019-12-02 Qinghai Liu , Xingxing Yu , Zhao Zhang

(NOTE: per referee comments, this article has been split; it is now superseded by "Existence of thread-wire minimizers" and "Near-wire thread-wire minimizers"; please see http://www.bkstephens.net.) Alt's thread problem asks for least-area…

Analysis of PDEs · Mathematics 2008-10-29 Benjamin K. Stephens

We consider a model of computation motivated by possible limitations on quantum computers. We have a linear array of n wires, and we may perform operations only on pairs of adjacent wires. Our goal is to build a circuits that perform…

Quantum Physics · Physics 2007-05-23 Samuel A. Kutin , David Petrie Moulton , Lawren M. Smithline

The girth of a graph is defined as the length of a shortest cycle in the graph. A $(k; g)$-cage is a graph of minimum order among all $k$-regular graphs with girth $g$. A cycle $C$ in a graph $G$ is termed nonseparating if the graph…

Combinatorics · Mathematics 2024-10-10 Xiang-Feng Pan , Jing-Zhong Mao , Hui-Qing Liu

An orbit of $G$ is a subset $S$ of $V(G)$ such that $\phi(u)=v$ for any two vertices $u,v\in S$, where $\phi$ is an isomorphism of $G$. The orbit number of a graph $G$, denoted by $\text{Orb}(G)$, is the number of orbits of $G$. In [A Note…

Discrete Mathematics · Computer Science 2017-08-01 Tzong-Huei Shiau , Yue-Li Wang , Kung-Jui Pai

Reliability assessment of interconnection networks is critical to the design and maintenance of multiprocessor systems. The $(n, k)$-enhanced hypercube $Q_{n,k}$, as a variation of the hypercube $Q_{n}$, was proposed by Tzeng and Wei in…

Combinatorics · Mathematics 2025-10-29 Yali Sun , Mingzu Zhang , Xing Feng , Xing Yang

We bound the volume of thick embeddings of finite graphs into the Heisenberg group, as well as the volume of coarse wirings of finite graphs into groups with polynomial growth. This work follows the work of Kolmogorov-Brazdin, Gromov-Guth…

Metric Geometry · Mathematics 2024-10-29 Or Kalifa

Let $G$ be a connected nonregular graphs of order $n$ with maximum degree $\Delta$ that attains the maximum spectral radius. Liu and Li (2008) proposed a conjecture stating that $G$ has a degree sequence $(\Delta,\ldots,\Delta,\delta)$ with…

Combinatorics · Mathematics 2024-11-27 Zejun Huang , Jiahui Liu , Chenxi Yang

Let $G$ be a graph, $C$ a longest cycle in $G$ and $\overline{p}$, $\overline{c}$ the lengths of a longest path and a longest cycle in $G\backslash C$, respectively. Almost all lower bounds for the circumference base on a standard…

Combinatorics · Mathematics 2009-07-16 Zh. G. Nikoghosyan

Let $G$ be a graph and $T$ a certain connected subgraph of $G$. The $T$-structure connectivity $\kappa(G; T)$ (or resp., $T$-substructure connectivity $\kappa^{s}(G; T)$) of $G$ is the minimum number of a set of subgraphs…

Combinatorics · Mathematics 2018-03-23 Dong Li , Xiaolan Hu , Huiqing Liu

We consider the problem of achieving average consensus in the minimum number of linear iterations on a fixed, undirected graph. We are motivated by the task of deriving lower bounds for consensus protocols and by the so-called "definitive…

Optimization and Control · Mathematics 2013-08-30 Julien M. Hendrickx , Raphaël M. Jungers , Alexander Olshevsky , Guillaume Vankeerberghen

We introduce a new graph invariant that measures fractional covering of a graph by cuts. Besides being interesting in its own right, it is useful for study of homomorphisms and tension-continuous mappings. We study the relations with…

Combinatorics · Mathematics 2015-11-24 Robert Šámal

We study graphs on $n$ vertices which have $2n-2$ edges and no proper induced subgraphs of minimum degree $3$. Erd\H{o}s, Faudree, Gy\'arf\'as, and Schelp conjectured that such graphs always have cycles of lengths $3,4,5,\dots, C(n)$ for…

Combinatorics · Mathematics 2014-08-25 Lothar Narins , Alexey Pokrovskiy , Tibor Szabó

In 2021, {\"O}. E\v{g}ecio\v{g}lu, V. Ir\v{s}i\v{c} introduced the concept of Fibonacci-run graph $\mathcal{R}_{n}$ as an induced subgraph of Hypercube. They conjectured that the diameter of $\mathcal{R}_{n}$ is given by…

Combinatorics · Mathematics 2024-01-29 Jianxin Wei , Yujun Yang

We give another version of Huang's proof that an induced subgraph of the n-dimensional cube graph containing over half the vertices has maximal degree at least $\sqrt{n}$, which implies the Sensitivity Conjecture. This argument uses…

Combinatorics · Mathematics 2019-09-04 Daniel V. Mathews

In 1982, Tuza conjectured that the size $\tau(G)$ of a minimum set of edges that intersects every triangle of a graph $G$ is at most twice the size $\nu(G)$ of a maximum set of edge-disjoint triangles of $G$. This conjecture was proved for…

Combinatorics · Mathematics 2024-05-21 Luis Chahua , Juan Gutierrez

The study of the diameter of the graph of polyhedra is a classical problem in the theory of linear programming. While transportation polytopes are at the core of operations research and statistics it is still open whether the Hirsch…

Combinatorics · Mathematics 2015-04-23 Steffen Borgwardt , Jesús A. De Loera , Elisabeth Finhold , Jacob Miller

The bandwidth of a graph is the labeling of vertices with minimum maximum edge difference. For many graph families this is NP-complete. A classic result computes the bandwidth for the hypercube. We generalize this result to give sharp lower…

Discrete Mathematics · Computer Science 2007-05-23 Tanya Y. Berger-Wolf , Mitchell A. Harris