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The Hoffman ratio bound, Lov\'{a}sz theta function and Schrijver theta function are classical upper bounds for the independence number of graphs, which are useful in graph theory, extremal combinatorics and information theory. By using…

Combinatorics · Mathematics 2025-02-19 Jiang Zhou

The analysis of signals defined over a graph is relevant in many applications, such as social and economic networks, big data or biological networks, and so on. A key tool for analyzing these signals is the so called Graph Fourier Transform…

Spectral Theory · Mathematics 2017-10-11 Stefania Sardellitti , Sergio Barbarossa , Paolo Di Lorenzo

This paper is a study of ``topological'' lower bounds for the chromatic number of a graph. Such a lower bound was first introduced by Lov\'asz in 1978, in his famous proof of the \emph{Kneser conjecture} via Algebraic Topology. This…

Combinatorics · Mathematics 2007-05-23 Jiri Matousek , Günter M. Ziegler

Our previous paper applied a lopsided version of the Lov\'asz Local Lemma that allows negative dependency graphs to the space of random injections from an $m$-element set to an $n$-element set. Equivalently, the same story can be told about…

Combinatorics · Mathematics 2014-02-25 Linyuan Lu , Laszlo A. Szekely

Non-commutative graph theory is an operator space generalization of graph theory. Well known graph parameters such as the independence number and Lov\'asz theta function were first generalized to this setting by Duan, Severini, and Winter.…

Operator Algebras · Mathematics 2017-09-19 Se-Jin Kim , Arthur Mehta

We introduce a novel technique to give bounds to the entangled value of non-local games. The technique is based on a class of graphs used by Cabello, Severini and Winter in 2010. The upper bound uses the famous Lov\'asz theta number and is…

Quantum Physics · Physics 2015-03-02 André Chailloux , Laura Mančinska , Giannicola Scarpa , Simone Severini

We recursively extend the Lov\'asz theta number to geometric hypergraphs on the unit sphere and on Euclidean space, obtaining an upper bound for the independence ratio of these hypergraphs. As an application we reprove a result in Euclidean…

Combinatorics · Mathematics 2022-05-25 Davi Castro-Silva , Fernando Mário de Oliveira Filho , Lucas Slot , Frank Vallentin

To each graph on $n$ vertices there is an associated subspace of the $n \times n$ matrices called the operator system of the graph. We prove that two graphs are isomorphic if and only if their corresponding operator systems are unitally…

Operator Algebras · Mathematics 2014-12-23 Carlos M. Ortiz , Vern I. Paulsen

The ring of graph invariants is spanned by the basic graph invariants which calculate the number of subgraphs isomorphic to a given graph in other graphs. These subgraphs counting invariants are not algebraically independent. In our view…

Combinatorics · Mathematics 2008-12-11 Tomi Mikkonen

The notion of duality is a key element in understanding the interplay between the stability and chromatic numbers of a graph. This notion is a central aspect in the celebrated theory of perfect graphs, and is further and deeply developed in…

Combinatorics · Mathematics 2020-04-21 Nathan Benedetto Proença , Marcel K. de Carli Silva , Gabriel Coutinho

Lov\'asz's bound to the capacity of a graph and the the sphere-packing bound to the probability of error in channel coding are given a unified presentation as information radii of the Csisz\'ar type using the R{\'e}nyi divergence in the…

Information Theory · Computer Science 2013-05-21 Marco Dalai

We consider the maximum independent set problem on graphs with maximum degree~$d$. We show that the integrality gap of the Lov\'asz $\vartheta$-function based SDP is $\widetilde{O}(d/\log^{3/2} d)$. This improves on the previous best result…

Data Structures and Algorithms · Computer Science 2015-04-24 Nikhil Bansal , Anupam Gupta , Guru Guruganesh

We prove a metric space scaling limit for a critical random graph with independent and identically distributed degrees having power-law tail behaviour with exponent $\alpha+1$, where $\alpha \in (1,2)$. The limiting components are…

Probability · Mathematics 2021-08-02 Guillaume Conchon--Kerjan , Christina Goldschmidt

We investigate the structure of conformally rigid graphs. Graphs are conformally rigid if introducing edge weights cannot increase (decrease) the second (last) eigenvalue of the Graph Laplacian. Edge-transitive graphs and distance-regular…

Combinatorics · Mathematics 2025-06-26 João Gouveia , Stefan Steinerberger , Rekha R. Thomas

The Lov\'asz Local Lemma is a powerful probabilistic technique for proving the existence of combinatorial objects. It is especially useful for colouring graphs and hypergraphs with bounded maximum degree. This paper presents a general…

Combinatorics · Mathematics 2021-04-14 Ian M. Wanless , David R. Wood

The linear complementarity problem is a continuous optimization problem that generalizes convex quadratic programming, Nash equilibria of bimatrix games and several such problems. This paper presents a continuous optimization formulation…

Discrete Mathematics · Computer Science 2018-10-19 Parthe Pandit , Ankur A. Kulkarni

A new characterization of the Lovasz theta function is provided by relating it to the (weighted) walk-generating function, thus establishing a relationship between two seemingly quite distinct concepts in algebraic graph theory. An…

Combinatorics · Mathematics 2025-02-24 Lasse Harboe Wolff

We show that any randomised Monte Carlo distributed algorithm for the Lov\'asz local lemma requires $\Omega(\log \log n)$ communication rounds, assuming that it finds a correct assignment with high probability. Our result holds even in the…

Distributed, Parallel, and Cluster Computing · Computer Science 2015-11-04 Sebastian Brandt , Orr Fischer , Juho Hirvonen , Barbara Keller , Tuomo Lempiäinen , Joel Rybicki , Jukka Suomela , Jara Uitto

A significant generalization of the Erd\"os-R\'enyi random graph model is an `inhomogeneous' random graph where the edge probabilities vary according to vertex types. We identify the threshold value for this random graph with a finite…

Probability · Mathematics 2024-11-06 Hamin Jung

We investigate the local chromatic number of shift graphs and prove that it is close to their chromatic number. This implies that the gap between the directed local chromatic number of an oriented graph and the local chromatic number of the…

Combinatorics · Mathematics 2009-06-17 Gábor Simonyi , Gábor Tardos