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Let G = (V,E) be an n-vertex graph and M_d a d-vertex graph, for some constant d. Is M_d a subgraph of G? We consider this problem in a model where all n processes are connected to all other processes, and each message contains up to O(log…

Distributed, Parallel, and Cluster Computing · Computer Science 2012-11-06 Danny Dolev , Christoph Lenzen , Shir Peled

We introduce and study level-planar straight-line drawings with a fixed number $\lambda$ of slopes. For proper level graphs, we give an $O(n \log^2 n / \log \log n)$-time algorithm that either finds such a drawing or determines that no such…

Data Structures and Algorithms · Computer Science 2019-08-02 Guido Brückner , Nadine Davina Krisam , Tamara Mchedlidze

Codes defined on graphs and their properties have been subjects of intense recent research. On the practical side, constructions for capacity-approaching codes are graphical. On the theoretical side, codes on graphs provide several…

Information Theory · Computer Science 2009-05-15 Srimathy Srinivasan , Andrew Thangaraj

Given a distribution of pebbles on the vertices of a graph, say that we can pebble a vertex if a pebble is left on it after some sequence of moves, each of which takes two pebbles from some vertex and places one on an adjacent vertex. A…

Combinatorics · Mathematics 2019-06-03 David Moews

A graph $G$ is $1$-extendible if every edge belongs to at least one $1$-factor of $G$. Let $G$ be a graph with a $1$-factor $F$. Then an even $F$-orientation of $G$ is an orientation in which each $F$-alternating cycle has exactly an even…

Combinatorics · Mathematics 2024-03-20 M. Abreu , D. Labbate , F. Romaniello , J. Sheehan

A graph G=(V,E) is representable if there exists a word W over the alphabet V such that letters x and y alternate in W if and only if (x,y) is in E for each x not equal to y. The motivation to study representable graphs came from algebra,…

Combinatorics · Mathematics 2011-08-09 Sergey Kitaev , Pavel Salimov , Christopher Severs , Henning Ulfarsson

We give superexponential lower and upper bounds on the number of coloured $d$-dimensional triangulations whose underlying space is an oriented manifold, when the number of simplices goes to infinity and $d\geq 3$ is fixed. In the special…

Combinatorics · Mathematics 2021-09-06 Guillaume Chapuy , Guillem Perarnau

We study the typical structure and the number of triangle-free graphs with $n$ vertices and $m$ edges where $m$ is large enough so that a typical triangle-free graph has a cut containing nearly all of its edges, but may not be bipartite.…

Combinatorics · Mathematics 2025-08-14 Matthew Jenssen , Will Perkins , Aditya Potukuchi

We show that expander graphs must have Gromov-hyperbolicity at least proportional to their diameter, with a constant of proportionality depending only on the expansion constant and maximal degree. In other words, expanders contain geodesic…

Combinatorics · Mathematics 2015-02-26 Anton Malyshev

We prove the following Alon-Boppana type theorem for general (not necessarily regular) weighted graphs: if $G$ is an $n$-node weighted undirected graph of average combinatorial degree $d$ (that is, $G$ has $dn/2$ edges) and girth $g>…

Discrete Mathematics · Computer Science 2017-07-21 Nikhil Srivastava , Luca Trevisan

We give a new lower bound on the expansion coefficient of an edge-vertex graph of a $d$-regular graph. As a consequence, we obtain an improvement on the lower bound on relative minimum distance of the expander codes constructed by Sipser…

Information Theory · Computer Science 2007-07-13 H. L. Janwa A. K. Lal

For a smooth expanding map $f$ of the circle, its (unmarked) length spectrum is defined as the set of logarithms of multipliers of periodic orbits of $f$. This spectrum is analogous to the set of lengths of all closed geodesics on…

Dynamical Systems · Mathematics 2025-11-24 Kostiantyn Drach , Vadim Kaloshin

We study Koebe orderings of planar graphs: vertex orderings obtained by modelling the graph as the intersection graph of pairwise internally-disjoint discs in the plane, and ordering the vertices by non-increasing radii of the associated…

Combinatorics · Mathematics 2022-01-25 Jesper Nederlof , Michał Pilipczuk , Karol Węgrzycki

An (edge) decomposition of a graph $G$ is a set of subgraphs of $G$ whose edge sets partition the edge set of $G$. Here we show, for each odd $\ell \geq 5$, that any graph $G$ of sufficiently large order $n$ with minimum degree at least…

Combinatorics · Mathematics 2024-11-27 Darryn Bryant , Peter Dukes , Daniel Horsley , Barbara Maenhaut , Richard Montgomery

We consider a random graph on a given degree sequence ${\cal D}$, satisfying certain conditions. We focus on two parameters $Q=Q({\cal D}), R=R({\cal D})$. Molloy and Reed proved that Q=0 is the threshold for the random graph to have a…

Combinatorics · Mathematics 2009-07-27 Hamed Hatami , Michael Molloy

The behavior of a certain random growth process is analyzed on arbitrary regular and non-regular graphs. Our argument is based on the Expander Mixing Lemma, which entails that the results are strongest for Ramanujan graphs, which…

Combinatorics · Mathematics 2019-10-23 Janko Boehm , Michael Joswig , Lars Kastner , Andrew Newman

A regular graph is co-edge regular if there exists a constant $\mu$ such that any two distinct and non-adjacent vertices have exactly $\mu$ common neighbors. In this paper, we show that for integers $s\ge 2$ and $n$ large enough, any…

Combinatorics · Mathematics 2019-08-09 Ying-Ying Tan , Jack H. Koolen , Zheng-Jiang Xia

The classic graphical Cheeger inequalities state that if $M$ is an $n\times n$ symmetric doubly stochastic matrix, then \[ \frac{1-\lambda_{2}(M)}{2}\leq\phi(M)\leq\sqrt{2\cdot(1-\lambda_{2}(M))} \] where…

Combinatorics · Mathematics 2019-09-30 Jenish C. Mehta , Leonard J. Schulman

We say that a $d$-regular graph is a $\gamma$-expander if for every not too large set of vertices $S$, there are at least $\gamma d |S|$ edges leaving $S$, and we say that a graph $G$ is $\gamma$-far from bipartite if at least $\gamma e(G)$…

Combinatorics · Mathematics 2026-05-15 Domagoj Bradač , Oliver Janzer

Let $G$ be a distance-regular graph of order $v$ and size $e$. In this paper, we show that the max-cut in $G$ is at most $e(1-1/g)$, where $g$ is the odd girth of $G$. This result implies that the independence number of $G$ is at most…

Combinatorics · Mathematics 2017-01-09 Sebastian M. Cioabă , Jack H. Koolen , Weiqiang Li