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Many important theorems in combinatorics, such as Szemer\'edi's theorem on arithmetic progressions and the Erd\H{o}s-Stone Theorem in extremal graph theory, can be phrased as statements about independent sets in uniform hypergraphs. In…

Combinatorics · Mathematics 2014-03-24 József Balogh , Robert Morris , Wojciech Samotij

Spectral embedding of graphs uses the top k non-trivial eigenvectors of the random walk matrix to embed the graph into R^k. The primary use of this embedding has been for practical spectral clustering algorithms [SM00,NJW02]. Recently,…

Probability · Mathematics 2018-09-10 Russell Lyons , Shayan Oveis Gharan

The K{\L}R conjecture of Kohayakawa, {\L}uczak, and R\"odl is a statement that allows one to prove that asymptotically almost surely all subgraphs of the random graph G_{n,p}, for sufficiently large p : = p(n), satisfy an embedding lemma…

Combinatorics · Mathematics 2016-02-22 D. Conlon , W. T. Gowers , W. Samotij , M. Schacht

In this note, we present a structural description of certain connected cographs having $k \geq 2$ main signless Laplacian eigenvalues. This result allows us to characterize the cographs which are quasi-threshold graphs with two main…

Combinatorics · Mathematics 2026-02-17 Átila Jones , Vilmar Trevisan , Cybele T. M. Vinagre

This is Part 2 in a series of papers about the growth of regular partitions in hereditary properties $3$-uniform hypergraphs. The focus of this paper is the notion of weak hypergraph regularity, first developed by Chung, Chung-Graham, and…

Combinatorics · Mathematics 2024-04-02 C. Terry

We consider the signless $p$-Laplacian of a graph, a generalisation of the usual signless Laplacian (the case $p=2$). We show a Perron-Frobenius property and basic inequalites for the largest eigenvalue and provide upper and lower bounds…

Combinatorics · Mathematics 2016-10-06 Elizandro Max Borba , Uwe Schwerdtfeger

Let $H$ be a $k$-uniform hypergraph with $n$ vertices. A {\em strong $r$-coloring} is a partition of the vertices into $r$ parts, such that each edge of $H$ intersects each part. A strong $r$-coloring is called {\em equitable} if the size…

Combinatorics · Mathematics 2007-05-23 Raphael Yuster

The spectrum of a graph is closely related to many graph parameters. In particular, the spectral gap of a regular graph which is the difference between its valency and second eigenvalue, is widely seen an algebraic measure of connectivity…

Combinatorics · Mathematics 2022-04-06 Sebastian M. Cioabă , Jack H. Koolen , Masato Mimura , Hiroshi Nozaki , Takayuki Okuda

A Cayley graph on the symmetric group $S_n$ is said to have the Aldous property if its strictly second largest eigenvalue (that is, the largest eigenvalue strictly smaller than the degree) is attained by the standard representation of…

Combinatorics · Mathematics 2025-10-29 Yuxuan Li , Binzhou Xia , Sanming Zhou

Here we study the spectral properties of an underlying weighted graph of a non-uniform hypergraph by introducing different connectivity matrices, such as adjacency, Laplacian and normalized Laplacian matrices. We show that different…

Combinatorics · Mathematics 2019-03-28 Anirban Banerjee

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

The eigenvalues of the Hamming graph $H(n,q)$ are known to be $\lambda_i(n,q)=(q-1)n-qi$, $0\leq i \leq n$. The characterization of equitable 2-partitions of the Hamming graphs $H(n,q)$ with eigenvalue $\lambda_{1}(n,q)$ was obtained by…

Combinatorics · Mathematics 2019-04-01 Ivan Mogilnykh , Alexandr Valyuzhenich

Motivated by the problem about HOMO-LUMO separation that arises in mathematical chemistry, Fowler and Pisanski introduced the notion of the HL-index which measures how large in absolute value may be the median eigenvalues of a graph. In…

Combinatorics · Mathematics 2014-01-10 Bojan Mohar

In this paper, we introduce the class of cored hypergraphs and power hypergraphs, and investigate the properties of their Laplacian H-eigenvalues. From an ordinary graph, one may generate a $k$-uniform hypergraph, called the $k$th power…

Spectral Theory · Mathematics 2013-04-26 Shenglong Hu , Liqun Qi , Jia-Yu Shao

In this paper, we give infinitely many examples of (non-isomorphic) connected $k$-regular graphs with smallest eigenvalue in half open interval $[-1-\sqrt2, -2)$ and also infinitely many examples of (non-isomorphic) connected $k$-regular…

Combinatorics · Mathematics 2011-05-30 Hyonju Yu

We prove two conjectures in spectral extremal graph theory involving the linear combinations of graph eigenvalues. Let $\lambda_1(G)$ be the largest eigenvalue of the adjacency matrix of a graph $G$, and $\bar{G}$ be the complement of $G$.…

Combinatorics · Mathematics 2022-06-09 Lele Liu

The $k$-dimensional Weisfeiler-Leman algorithm ($k$-WL) is a fruitful approach to the Graph Isomorphism problem. 2-WL corresponds to the original algorithm suggested by Weisfeiler and Leman over 50 years ago. 1-WL is the classical color…

Discrete Mathematics · Computer Science 2019-04-10 V. Arvind , Frank Fuhlbrück , Johannes Köbler , Oleg Verbitsky

The $k$-dimensional Weisfeiler-Leman procedure ($k$-WL), which colors $k$-tuples of vertices in rounds based on the neighborhood structure in the graph, has proven to be immensely fruitful in the algorithmic study of Graph Isomorphism. More…

Computational Complexity · Computer Science 2020-06-08 V. Arvind , Frank Fuhlbrück , Johannes Köbler , Oleg Verbitsky

In the broad range of studies related to quantum graphs, quantum graph spectra appear as a topic of special interest. They are important in the context of diffusion type problems posed on metric graphs. Theoretical findings suggest that…

Numerical Analysis · Mathematics 2023-12-15 Chong-Son Dröge , Anna Weller

An $r$-cut of a $k$-uniform hypergraph is a partition of its vertex set into $r$ parts, and the size of the cut is the number of edges which have at least one vertex in each part. The study of the possible size of the largest $r$-cut in a…

Combinatorics · Mathematics 2025-11-12 Oliver Janzer , Julien Portier
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