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We describe two constructions of (very) dense graphs which are edge disjoint unions of large {\em induced} matchings. The first construction exhibits graphs on $N$ vertices with ${N \choose 2}-o(N^2)$ edges, which can be decomposed into…

Combinatorics · Mathematics 2011-11-09 Noga Alon , Ankur Moitra , Benny Sudakov

High triangle density -- the graph property stating that a constant fraction of two-hop paths belong to a triangle -- is a common signature of social networks. This paper studies triangle-dense graphs from a structural perspective. We prove…

Data Structures and Algorithms · Computer Science 2014-02-10 Rishi Gupta , Tim Roughgarden , C. Seshadhri

We introduce a new parameter, called stretch-width, that we show sits strictly between clique-width and twin-width. Unlike the reduced parameters [BKW '22], planar graphs and polynomial subdivisions do not have bounded stretch-width. This…

Discrete Mathematics · Computer Science 2023-05-23 Édouard Bonnet , Julien Duron

We initiate the study of diameter computation in geometric intersection graphs from the fine-grained complexity perspective. A geometric intersection graph is a graph whose vertices correspond to some shapes in $d$-dimensional Euclidean…

Computational Geometry · Computer Science 2022-03-11 Karl Bringmann , Sándor Kisfaludi-Bak , Marvin Künnemann , André Nusser , Zahra Parsaeian

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

In this paper we completely characterize the graphs which have an edge weighted adjacency matrix belonging to the class of $n \times n$ involutions with spectrum equal to $\{ \lambda_1^{n-2}, \lambda_2^{2} \}$ for some $\lambda_1$ and some…

Combinatorics · Mathematics 2015-04-17 Karen Meagher , Irene Sciriha

Asymptotic properties of random regular graphs are object of extensive study in mathematics. In this note we argue, based on theory of spin glasses, that in random regular graphs the maximum cut size asymptotically equals the number of…

Disordered Systems and Neural Networks · Physics 2010-02-25 Lenka Zdeborová , Stefan Boettcher

In this note, we consider the problem of finding a step-by-step transformation between two longest increasing subsequences in a sequence, namely Longest Increasing Subsequence Reconfiguration. We give a polynomial-time algorithm for…

Data Structures and Algorithms · Computer Science 2023-10-03 Yuuki Aoike , Masashi Kiyomi , Yasuaki Kobayashi , Yota Otachi

Since the introduction of the Hermitian adjacency matrix for digraphs, interest in so-called complex unit gain graphs has surged. In this work, we consider gain graphs whose spectra contain the minimum number of two distinct eigenvalues.…

Combinatorics · Mathematics 2021-05-20 Pepijn Wissing , Edwin R. van Dam

A graph $G$ is a prime distance graph (respectively, a 2-odd graph) if its vertices can be labeled with distinct integers such that for any two adjacent vertices, the difference of their labels is prime (either 2 or odd). We prove that…

Combinatorics · Mathematics 2021-06-07 Joshua D. Laison , Colin Starr , Andrea Walker

In a reduction sequence of a graph, vertices are successively identified until the graph has one vertex. At each step, when identifying $u$ and $v$, each edge incident to exactly one of $u$ and $v$ is coloured red. Bonnet, Kim, Thomass\'e…

Combinatorics · Mathematics 2025-10-28 Édouard Bonnet , O-joung Kwon , David R. Wood

The GG-width of a class of graphs GG is defined as follows. A graph G has GG-width k if there are k independent sets N1,...,Nk in G such that G can be embedded into a graph H in GG such that for every edge e in H which is not an edge in G,…

Combinatorics · Mathematics 2012-11-01 M. Chang , L. Hung , T. Kloks , S. Peng

A bar 1-visibility drawing of a graph $G$ is a drawing of $G$ where each vertex is drawn as a horizontal line segment called a bar, each edge is drawn as a vertical line segment where the vertical line segment representing an edge must…

Discrete Mathematics · Computer Science 2013-02-21 Shaheena Sultana , Md. Saidur Rahman , Arpita Roy , Suraiya Tairin

Clique-width is a well-studied graph parameter owing to its use in understanding algorithmic tractability: if the clique-width of a graph class ${\cal G}$ is bounded by a constant, a wide range of problems that are NP-complete in general…

Combinatorics · Mathematics 2021-12-23 Konrad K. Dabrowski , Matthew Johnson , Daniël Paulusma

Two permutations of the vertices of a graph $G$ are called $G$-different if there exists an index $i$ such that $i$-th entry of the two permutations form an edge in $G$. We bound or determine the maximum size of a family of pairwise…

Combinatorics · Mathematics 2017-03-01 Louis Golowich , Chiheon Kim , Richard Zhou

We study the existence of polynomial kernels, for parameterized problems without a polynomial kernel on general graphs, when restricted to graphs of bounded twin-width. Our main result is that a polynomial kernel for $k$-Dominating Set on…

Data Structures and Algorithms · Computer Science 2021-09-15 Édouard Bonnet , Eun Jung Kim , Amadeus Reinald , Stéphan Thomassé , Rémi Watrigant

Computer or communication networks are so designed that they do not easily get disrupted under external attack and, moreover, these are easily reconstructible if they do get disrupted. These desirable properties of networks can be measured…

Combinatorics · Mathematics 2011-09-23 T. C. E. Cheng , Yinkui Li , Chuandong Xu , Shenggui Zhang

A universal representation theorem is derived that shows any graph is the intersection graph of one chordal graph, a number of co-bipartite graphs, and one unit interval graph. Central to the the result is the notion of the clique cover…

Combinatorics · Mathematics 2015-04-21 Farhad Shahrokhi

We study connected graphs with a fixed degree sequence, in the sparse setting where the number of edges grows linearly in the number of vertices. Using the relation to the configuration model, we identify the number of such connected graphs…

Combinatorics · Mathematics 2026-05-11 Sasha Bell , Serte Donderwinkel , Remco van der Hofstad

The intersection graph of a collection of trapezoids with corner points lying on two parallel lines is called a trapezoid graph. Using binary indexed tree data structure, we improve algorithms for calculating the size and the number of…

Data Structures and Algorithms · Computer Science 2011-06-14 Aleksandar Ilic , Andreja Ilic