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For a finite simple graph $G$ we give an upper bound for the regularity of the powers of the edge ideal $I(G)$.

Commutative Algebra · Mathematics 2018-10-16 Jürgen Herzog , Takayuki Hibi

Let $\mathcal{B}(n,q)$ be the class of block graphs on $n$ vertices having all their blocks of the same size. We prove that if $G\in \mathcal{B}(n,q)$ has at most three pairwise adjacent cut vertices then the minimum spectral radius…

Spectral Theory · Mathematics 2020-10-15 Cristian M. Conde , Ezequiel Dratman , Luciano N. Grippo

Using ergodic theory, in this paper we present a Gel'fand-type spectral radius formula which states that the joint spectral radius is equal to the generalized spectral radius for a matrix multiplicative semigroup $\bS^+$ restricted to a…

Optimization and Control · Mathematics 2011-07-04 Xiongping Dai

Let $(n^+, n^0, n^-)$ denote the inertia of a graph $G$ with $n$ vertices. Nordhaus-Gaddum bounds are known for inertia, except for an upper bound for $n^-$. We conjecture that for any graph \[ n^-(G) + n^-(\bar{G}) \le 1.5(n - 1), \] and…

Combinatorics · Mathematics 2019-03-05 Pawel Wocjan , Clive Elphick

We prove that for $k\geq 3$, the bound given by Brooks' theorem on the chromatic number of $k$-th powers of graphs of maximum degree $\Delta \geq 3$ can be lowered by 1, even in the case of online list coloring.

Discrete Mathematics · Computer Science 2013-10-22 Marthe Bonamy , Nicolas Bousquet

We investigate spectral properties of quantum graphs in the form of a periodic chain of rings with a connecting link between each adjacent pair, assuming that wave functions at the vertices are matched through conditions manifestly…

Mathematical Physics · Physics 2022-07-12 Marzieh Baradaran , Pavel Exner , Milos Tater

We analyze the convergence of the spectrum of large random graphs to the spectrum of a limit infinite graph. We apply these results to graphs converging locally to trees and derive a new formula for the Stieljes transform of the spectral…

Probability · Mathematics 2009-05-05 Charles Bordenave , Marc Lelarge

This paper presents bounds for the variation of the spectral radius $\lambda(G)$ of a graph $G$ after some perturbations or local vertex/edge modifications of $G$. The perturbations considered here are the connection of a new vertex with,…

Combinatorics · Mathematics 2012-09-25 C. Dalfó , M. A. Fiol , E. Garriga

Let $G$ be an irregular graph on $n$ vertices with maximum degree $\Delta$ and diameter $D$. We show that \Delta-\lambda_1>\frac{1}{nD} where $\lambda_1$ is the largest eigenvalue of the adjacency matrix of $G$. We also study the effect of…

Combinatorics · Mathematics 2007-05-23 Sebastian M. Cioabă

In 1962, Erd\H{o}s gave a sufficient condition for Hamilton cycles in terms of the vertex number, edge number, and minimum degree of graphs which generalized Ore's theorem. One year later, Moon and Moser gave an analogous result for…

Combinatorics · Mathematics 2016-11-30 Binlong Li , Bo Ning

In this paper we determine the unique graph with minimum distance spectral radius among all connected graphs of fixed order and given edge connectivity.

Combinatorics · Mathematics 2014-09-19 Xiao-Xin Li , Yi-Zheng Fan , Yi Wang

The famous Gelfand formula $\rho(A)= \limsup_{n\to\infty}\|A^{n}\|^{1/n}$ for the spectral radius of a matrix is of great importance in various mathematical constructions. Unfortunately, the range of applicability of this formula is…

Rings and Algebras · Mathematics 2009-09-13 Victor Kozyakin

A well known upper bound for the independence number $\alpha(G)$ of a graph $G$, due to Cvetkovi\'{c}, is that \begin{equation*} \alpha(G) \le n^0 + \min\{n^+ , n^-\} \end{equation*} where $(n^+, n^0, n^-)$ is the inertia of $G$. We prove…

Combinatorics · Mathematics 2021-10-05 Pawel Wocjan , Clive Elphick , Aida Abiad

Using multiplicative ergodic theory we prove two formulae describing the relationships between different joint spectral radii for sets of bounded linear operators acting on a Banach space. In particular we recover a formula previously…

Dynamical Systems · Mathematics 2009-06-17 Ian D. Morris

We prove distance bounds for graphs possessing positive Bakry-\'Emery curvature apart from an exceptional set, where the curvature is allowed to be non-positive. If the set of non-positively curved vertices is finite, then the graph admits…

Differential Geometry · Mathematics 2019-03-26 Shiping Liu , Florentin Münch , Norbert Peyerimhoff , Christian Rose

We investigate spectral quantities of quantum graphs by expanding them as sums over pseudo orbits, sets of periodic orbits. Only a finite collection of pseudo orbits which are irreducible and where the total number of bonds is less than or…

Mathematical Physics · Physics 2015-06-05 Ram Band , Jonathan M. Harrison , Christopher H. Joyner

In this paper, we determine the graphs whose spectral radius and distance spectral radius attain maximum and minimum among all complements of clique trees. Furthermore, we also determine the graphs whose spectral radius and distance…

Combinatorics · Mathematics 2024-05-31 Xu Chen , Dongjun Fan , Rongxiao Shao , Guoping Wang

We give a proof for sharp estimate for the number of spanning trees using linear algebra and generalize this bound to multigraphs. In addition, we show that this bound is tight for complete graphs. In addition, we give estimates for number…

Combinatorics · Mathematics 2022-12-01 K. V. Chelpanov

In this paper we show that in some cases the E.Hopf rigidity phenomenon admits quantitative interpretation. More precisely we estimate from above the measure of the set $\mathcal{M}$ swept by minimal orbits. These estimates are sharp, i.e.…

Dynamical Systems · Mathematics 2014-05-09 Michael , Bialy

We establish an Expander Mixing Lemma for directed graphs in terms of the eigenvalues of an associated asymmetric transition probability matrix, extending the classical spectral inequality to the asymmetric setting. As an application, we…

Combinatorics · Mathematics 2025-11-04 Rebecca Carter
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