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This paper generalizes and unifies the existing spectral bounds on the $k$-independence number of a graph, which is the maximum size of a set of vertices at pairwise distance greater than $k$. The previous bounds known in the literature…

Combinatorics · Mathematics 2018-08-28 A. Abiad , G. Coutinho , M. A. Fiol

We present a number of relations involving the number of cliques in a graph and its spectral radius.

Combinatorics · Mathematics 2007-05-23 Bela Bollobas , Vladimir Nikiforov

In this paper, we obtain two spectral upper bounds for the $k$-independence number of a graph which is is the maximum size of a set of vertices at pairwise distance greater than $k$. We construct graphs that attain equality for our first…

Combinatorics · Mathematics 2016-08-19 Aida Abiad , Sebastian Cioabă , Michael Tait

Hypergraphs are an invaluable tool to understand many hidden patterns in large data sets. Among many ways to represent hypergraph, one useful representation is that of weighted clique expansion. In this paper, we consider this…

Combinatorics · Mathematics 2018-08-15 Ashwin Guha , Ambedkar Dukkipati

We improve recent results relating graph eigenvalues to other graph parameters like girth, domination number, and minimum degree.

Combinatorics · Mathematics 2007-05-23 Vladimir Nikiforov

We determine new upper bounds for the clique numbers of strongly regular graphs in terms of their parameters. These bounds improve on the Delsarte bound for infinitely many feasible parameter tuples for strongly regular graphs, including…

Combinatorics · Mathematics 2019-01-31 Gary R. W. Greaves , Leonard H. Soicher

We give lower bounds on the size and total size of clique partitions of a graph in terms of its spectral radius and minimum degree, and derive a spectral upper bound for the maximum number of edge-disjoint $t$-cliques. The extremal graphs…

Combinatorics · Mathematics 2021-11-05 Jiang Zhou , Edwin R. van Dam

We generalize the concept of token graphs to obtain supertoken graphs. In the latter case, there can be more than one token in a vertex. We formally define supertoken graphs and establish their basic properties. Moreover, we provide some…

Combinatorics · Mathematics 2026-04-08 Mónica A. Reyes , Cristina Dalfó , Miquel Àngel Fiol

We give a bound on the spectral radius of subgraphs of regular graphs with given order and diameter. We give a lower bound on the smallest eigenvalue of a nonbipartite regular graph of given order and diameter.

Combinatorics · Mathematics 2007-05-25 Vladimir Nikiforov

We define the independence ratio and the chromatic number for bounded, self-adjoint operators on an L^2-space by extending the definitions for the adjacency matrix of finite graphs. In analogy to the Hoffman bounds for finite graphs, we…

Functional Analysis · Mathematics 2014-10-07 Christine Bachoc , Evan DeCorte , Fernando Mario de Oliveira Filho , Frank Vallentin

We establish new bounds on the minimum number of distinct eigenvalues among real symmetric matrices with nonzero off-diagonal pattern described by the edges of a graph and apply these to determine the minimum number of distinct eigenvalues…

Combinatorics · Mathematics 2018-11-19 Beth Bjorkman , Leslie Hogben , Scarlitte Ponce , Carolyn Reinhart , Theodore Tranel

In this paper, we give spectral upper bounds for the independence number of even uniform hypergraphs and graphs, extend the Hoffman bound to even uniform hypergraphs, and give a simple spectral condition for determining the independence…

Combinatorics · Mathematics 2026-03-10 Xinyu Hu , Jiang Zhou , Changjiang Bu

We study the behaviour of clique complexes of graphs under the operation of taking graph powers. As an example we compute the clique complexes of powers of cycles, or, in other words, the independence complexes of circular complete graphs.

Combinatorics · Mathematics 2015-03-19 Michal Adamaszek

We prove an upper bound for the independence number of a graph in terms of the largest Laplacian eigenvalue, and of a certain induced subgraph. Our bound is a refinement of a well-known Hoffman-type bound.

Combinatorics · Mathematics 2023-11-17 Bogdan Nica

It is well known that $n/(n - \mu)$, where $\mu$ is the spectral radius of a graph with $n$ vertices, is a lower bound for the clique number. We conjecture that $\mu$ can be replaced in this bound with $\sqrt{s^+}$, where $s^+$ is the sum…

Combinatorics · Mathematics 2018-08-10 Clive Elphick , Pawel Wocjan

We give upper and lower bounds on the spectral radius of a graph in terms of the number of walks. We generalize a number of known results.

Combinatorics · Mathematics 2007-05-23 Vladimir Nikiforov

For signed graphs we provide a cubic polynomial upper bound on the multiplicity of its eigenvalues. We show that this bound is sharp by providing examples of signed graphs in which it is attained. We also discuss particular cases in which…

Combinatorics · Mathematics 2019-11-05 Farzaneh Ramezani , Peter Rowlinson , Zoran Stanic

In this article we present the idea of clique ceiling numbers of the vertices of a given graph that has a universal vertex. We follow up with a polynomial-time algorithm to compute an upper bound for the clique number of such a graph using…

Combinatorics · Mathematics 2019-06-04 R. Dharmarajan , D. Ramachandran

We propose new bounds on the domination number and on the independence number of a graph and show that our bounds compare favorably to recent ones. Our bounds are obtained by using the Bhatia-Davis inequality linking the variance, the…

Combinatorics · Mathematics 2022-01-25 Jochen Harant , Samuel Mohr

We derive bounds on the size of an independent set based on eigenvalues. This generalizes a result due to Delsarte and Hoffman. We use this to obtain new bounds on the independence number of the Erd\H{o}s-R\'{e}nyi graphs. We investigate…

Combinatorics · Mathematics 2007-05-23 C. D. Godsil , M. W. Newman
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