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Motivated both by recently introduced forms of list colouring and by earlier work on independent transversals subject to a local sparsity condition, we use the semi-random method to prove the following result. For any function $\mu$…

Combinatorics · Mathematics 2021-08-16 Ross J. Kang , Tom Kelly

Finding the stability number of a graph, i.e., the maximum number of vertices of which no two are adjacent, is a well known NP-hard combinatorial optimization problem. Since this problem has several applications in real life, there is need…

Optimization and Control · Mathematics 2022-03-15 Elisabeth Gaar , Melanie Siebenhofer , Angelika Wiegele

Given $d>0$ and a positive integer $n$, let $G$ be a triangle-free graph on $n$ vertices with average degree $d$. With an elegant induction, Shearer (1983) tightened a seminal result of Ajtai, Koml\'os and Szemer\'edi (1980/1981) by proving…

Combinatorics · Mathematics 2025-03-14 Pjotr Buys , Jan van den Heuvel , Ross J. Kang

We show that for any graph $G$, by considering "activation" through the strong product with another graph $H$, the relation $\alpha(G) \leq \vartheta(G)$ between the independence number and the Lov\'{a}sz number of $G$ can be made…

Combinatorics · Mathematics 2017-01-06 Antonio Acín , Runyao Duan , David E. Roberson , Ana Belén Sainz , Andreas Winter

Let $B(2d-1, d)$ be the subgraph of the hypercube $\mathcal{Q}_{2d-1}$ induced by its two largest layers. Duffus, Frankl and R\"odl proposed the problem of finding the asymptotics for the logarithm of the number of maximal independent sets…

Combinatorics · Mathematics 2025-05-02 József Balogh , Ce Chen , Ramon I. Garcia

The stability number of a graph $G$, denoted as $\alpha(G)$, is the maximum size of an independent (stable) set in $G$. Semidefinite programming (SDP) methods, which originated from Lov\'asz's theta number and expanded through…

Optimization and Control · Mathematics 2025-09-11 Luis Felipe Vargas , Juan C. Vera , Peter J. C. Dickinson

This paper delves into three research directions, leveraging the Lov\'{a}sz $\vartheta$-function of a graph. First, it focuses on the Shannon capacity of graphs, providing new results that determine the capacity for two infinite subclasses…

Combinatorics · Mathematics 2024-04-30 Igal Sason

We give a deterministic, nearly logarithmic-space algorithm for mild spectral sparsification of undirected graphs. Given a weighted, undirected graph $G$ on $n$ vertices described by a binary string of length $N$, an integer $k\leq \log n$,…

Data Structures and Algorithms · Computer Science 2020-04-21 Dean Doron , Jack Murtagh , Salil Vadhan , David Zuckerman

The theta function of Lovasz is a graph parameter that can be computed up to arbitrary precision in polynomial time. It plays a key role in algorithms that approximate graph parameters such as maximum independent set, maximum clique and…

Data Structures and Algorithms · Computer Science 2025-06-04 Uriel Feige , Vadim Grinberg

We introduce a generalization of the celebrated Lov\'asz theta number of a graph to simplicial complexes of arbitrary dimension. Our generalization takes advantage of real simplicial cohomology theory, in particular combinatorial…

Combinatorics · Mathematics 2017-04-07 Christine Bachoc , Anna Gundert , Alberto Passuello

Our main result is a formulation and proof of the reverse hypercontractive inequality in the sum-of-squares (SOS) proof system. As a consequence we show that for any constant $0 < \gamma \leq 1/4$, the SOS/Lasserre SDP hierarchy at degree…

Computational Complexity · Computer Science 2016-03-03 Manuel Kauers , Ryan O'Donnell , Li-Yang Tan , Yuan Zhou

Fomin and Villanger (STACS 2010) proved that Maximum Independent Set, Feedback Vertex Set, and more generally the problem of finding a maximum induced subgraph of treewith at most a constant $t$, can be solved in polynomial time on graph…

Data Structures and Algorithms · Computer Science 2016-07-18 Pedro Montealegre , Ioan Todinca

Sparse-dense partitions was introduced by Feder, Hell, Klein, and Motwani [STOC 1999, SIDMA 2003] as a tool to solve partitioning problems. In this paper, the following result concerning independent sets in graphs having sparse-dense…

Discrete Mathematics · Computer Science 2022-08-10 Uéverton S. Souza

We study the algorithmic problem of finding large $\gamma$-balanced independent sets in dense random bipartite graphs; an independent set is $\gamma$-balanced if a $\gamma$ proportion of its vertices lie on one side of the bipartition. In…

Data Structures and Algorithms · Computer Science 2025-09-12 Abhishek Dhawan , Eren C. Kızıldağ , Neeladri Maitra

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

The maximum independent set problem is one of the most important problems in graph algorithms and has been extensively studied in the line of research on the worst-case analysis of exact algorithms for NP-hard problems. In the weighted…

Data Structures and Algorithms · Computer Science 2021-08-31 Sen Huang , Mingyu Xiao , Xiaoyu Chen

An $n$-vertex, $d$-regular graph can have at most $2^{n/2+o_d(n)}$ independent sets. In this paper we address what happens with this upper bound when we impose the further condition that the graph has independence number at most $\alpha$.…

Combinatorics · Mathematics 2024-10-29 David Galvin , Phillip Marmorino

In this note we consider a more general version of local sparsity introduced recently by Anderson, Kuchukova, and the author. In particular, we say a graph $G = (V, E)$ is $(k, r)$-locally-sparse if for each vertex $v \in V(G)$, the…

Combinatorics · Mathematics 2025-07-22 Abhishek Dhawan

We study the class of independence complexes of claw-free graphs. The main theorem give good bounds on the connectivity of these complexes, given bounds for a few subcomplexes of the same class. Two applications are presented. Firstly, we…

Combinatorics · Mathematics 2007-05-23 Alexander Engström

This paper presents a linear prioritized local algorithm that computes large independent sets on a random $d$-regular graph with small and fixed degree $d$. We studied experimentally the independence ratio obtained by the algorithm when $ d…

Data Structures and Algorithms · Computer Science 2021-08-18 Raffaele Marino , Scott Kirkpatrick