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We construct an infinite family of bounded-degree bipartite unique-neighbour expander graphs with arbitrarily unbalanced sides. Although weaker than the lossless expanders constructed by Capalbo et al., our construction is simpler and may…

Combinatorics · Mathematics 2023-01-10 Ron Asherov , Irit Dinur

We revisit the classical question of the relationship between the diameter of a graph and its expansion properties. One direction is well understood: expander graphs exhibit essentially the lowest possible diameter. We focus on the reverse…

Combinatorics · Mathematics 2017-11-23 Michael Dinitz , Michael Schapira , Gal Shahaf

We give an elementary proof for new strict upper and lower bounds for the correction term in Ramanujan's approximation for the factorial function

Classical Analysis and ODEs · Mathematics 2012-12-07 Michael D. Hirschhorn , Mark B. Villarino

Extremal graph theory studies the maximum or minimum number of subgraphs isomorphic to a prescribed graph under given constraints. \textit{Localization} has recently emerged as a framework that refines such problems by assigning extremal…

Combinatorics · Mathematics 2026-03-10 Rajat Adak , L. Sunil Chandran

We provide a new constant factor approximation algorithm for the (connected) distance-$r$ dominating set problem on graph classes of bounded expansion. Classes of bounded expansion include many familiar classes of sparse graphs such as…

Distributed, Parallel, and Cluster Computing · Computer Science 2018-06-08 Saeed Akhoondian Amiri , Patrice Ossona de Mendez , Roman Rabinovich , Sebastian Siebertz

It has long been known that random regular graphs are with high probability good expanders. This was first established in the 1980s by Bollob\'as by directly calculating the probability that a set of vertices has small expansion and then…

Discrete Mathematics · Computer Science 2012-11-05 Michael Lampis

Reidl, S\'anchez Villaamil, and Stravopoulos (2019) characterized graph classes of bounded expansion as follows: A class $\mathcal{C}$ closed under subgraphs has bounded expansion if and only if there exists a function $f:\mathbb{N} \to…

Combinatorics · Mathematics 2024-11-05 Gwenaël Joret , Clément Rambaud

This is the fifth in a series of articles devoted to showing that a typical covering map of large degree to a fixed, regular graph has its new adjacency eigenvalues within the bound conjectured by Alon for random regular graphs. In this…

Discrete Mathematics · Computer Science 2019-11-18 Joel Friedman , David Kohler

In this paper, we determine the bound of the valency of the odd circulant graph which guarantees to be a Ramanujan graph for each fixed number of vertices. In almost of the cases, the bound coincides with the trivial bound, which comes from…

Number Theory · Mathematics 2015-03-16 Miki Hirano , Kohei Katata , Yoshinori Yamasaki

We enumerate factorisations of the complete bipartite graph into spanning semiregular graphs in several cases, including when the degrees of all the factors except one or two are small. The resulting asymptotic behaviour is seen to…

Combinatorics · Mathematics 2022-12-21 Mahdieh Hasheminezhad , Brendan D. McKay

An $(n,d,\lambda)$-graph is a $d$ regular graph on $n$ vertices in which the absolute value of any nontrivial eigenvalue is at most $\lambda$. For any constant $d \geq 3$, $\epsilon>0$ and all sufficiently large $n$ we show that there is a…

Combinatorics · Mathematics 2020-03-27 Noga Alon

Classes of graphs with bounded expansion are a generalization of both proper minor closed classes and degree bounded classes. Such classes are based on a new invariant, the greatest reduced average density (grad) of G with rank r,…

Combinatorics · Mathematics 2007-05-23 Jaroslav Nesetril , Patrice Ossona De Mendez

It was recently proved that every planar graph is a subgraph of the strong product of a path and a graph with bounded treewidth. This paper surveys generalisations of this result for graphs on surfaces, minor-closed classes, various…

Combinatorics · Mathematics 2021-02-18 Zdeněk Dvořák , Tony Huynh , Gwenaël Joret , Chun-Hung Liu , David R. Wood

Factor graphs are important models for succinctly representing probability distributions in machine learning, coding theory, and statistical physics. Several computational problems, such as computing marginals and partition functions, arise…

Machine Learning · Computer Science 2017-08-09 Damian Straszak , Nisheeth K. Vishnoi

We consider families of finite quantum graphs of increasing size and we are interested in how eigenfunctions are distributed over the graph. As a measure for the distribution of an eigenfunction on a graph we introduce the entropy, it has…

Mathematical Physics · Physics 2014-05-23 Lionel Kameni , Roman Schubert

In the study of deterministic distributed algorithms it is commonly assumed that each node has a unique $O(\log n)$-bit identifier. We prove that for a general class of graph problems, local algorithms (constant-time distributed algorithms)…

Distributed, Parallel, and Cluster Computing · Computer Science 2013-12-24 Mika Göös , Juho Hirvonen , Jukka Suomela

We study the problem of graph clustering where the goal is to partition a graph into clusters, i.e. disjoint subsets of vertices, such that each cluster is well connected internally while sparsely connected to the rest of the graph. In…

Data Structures and Algorithms · Computer Science 2021-12-17 Thatchaphol Saranurak , Di Wang

We relate two important notions in graph theory: expanders which are highly connected graphs, and modularity a parameter of a graph that is primarily used in community detection. More precisely, we show that a graph having modularity…

Combinatorics · Mathematics 2023-12-13 Baptiste Louf , Colin McDiarmid , Fiona Skerman

Extending a previous result of the first two authors, we prove a local limit theorem for the joint distribution of subgraph counts in the Erd\H{o}s-R\'{e}nyi random graph $G(n,p)$. This limit can be described as a nonlinear transformation…

Probability · Mathematics 2024-12-13 Ashwin Sah , Mehtaab Sawhney , Daniel G. Zhu

We show that the local weak limit of a sequence of finite expander graphs with uniformly bounded degree is an ergodic (or extremal) unimodular random graph. In particular, the critical probability of percolation of the limiting random graph…

Probability · Mathematics 2021-05-12 Sourav Sarkar