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In this work, we study the problem of computing a maximum common contraction of two vertex-labeled graphs, i.e. how to make them identical by contracting as little edges as possible in the two graphs. We study the problem from a…

Data Structures and Algorithms · Computer Science 2025-07-01 Manuel Lafond , Bertrand Marchand

Using connections to random matrix theory and orthogonal polynomials, we develop a framework for obtaining explicit closed-form formulae for the number, $\mathscr{N}_{g}(2\nu,j)$, of connected $2\nu$-valent labeled graphs with $j$ vertices…

Combinatorics · Mathematics 2025-09-19 Roozbeh Gharakhloo , Tomas Lasic Latimer

A fundamental theorem of Laman characterises when a bar-joint framework realised generically in the Euclidean plane admits a non-trivial continuous deformation of its vertices. This has recently been extended in two ways. Firstly to…

Metric Geometry · Mathematics 2015-07-31 Anthony Nixon , Bernd Schulze

We define the class of high dimensional graph manifolds. These are compact smooth manifolds supporting a decomposition into finitely many pieces, each of which is diffeomorphic to the product of a torus with a finite volume hyperbolic…

Differential Geometry · Mathematics 2016-03-22 Roberto Frigerio , Jean-Francois Lafont , Alessandro Sisto

Using a probabilistic method, we prove that $d(d+1)$-connected graphs are rigid in $\mathbb{R}^d$, a conjecture of Lov\'asz and Yemini. Then, using recent results on weakly globally linked pairs, we modify our argument to prove that…

Combinatorics · Mathematics 2023-12-05 Soma Villányi

We investigate the tractability of a simple fusion of two fundamental structures on graphs, a spanning tree and a perfect matching. Specifically, we consider the following problem: given an edge-weighted graph, find a minimum-weight…

Data Structures and Algorithms · Computer Science 2024-07-12 Kristóf Bérczi , Tamás Király , Yusuke Kobayashi , Yutaro Yamaguchi , Yu Yokoi

A simple graph is $3$-rigid if its generic bar-joint frameworks in $R^3$ are infinitesimally rigid. Necessary and sufficient conditions are obtained for the minimal $3$-rigidity of a simple graph which is obtained from the $1$-skeleton of a…

Combinatorics · Mathematics 2015-09-03 James Cruickshank , Derek Kitson , Stephen Power

A simple graph G=(V,E) is 3-rigid if its generic bar-joint frameworks in R3 are infinitesimally rigid. Block and hole graphs are derived from triangulated spheres by the removal of edges and the addition of minimally rigid subgraphs, known…

Combinatorics · Mathematics 2015-07-10 James Cruickshank , Derek Kitson , Stephen Power

We develop a bipartite rigidity theory for bipartite graphs parallel to the classical rigidity theory for general graphs, and define for two positive integers $k,l$ the notions of $(k,l)$-rigid and $(k,l)$-stress free bipartite graphs. This…

Combinatorics · Mathematics 2014-07-15 Gil Kalai , Eran Nevo , Isabella Novik

We consider the problem of finding an inductive construction, based on vertex splitting, of triangulated spheres with a fixed number of additional edges (braces). We show that for any positive integer $b$ there is such an inductive…

Combinatorics · Mathematics 2021-07-09 James Cruickshank , Eleftherios Kastis , Derek Kitson , Bernd Schulze

This paper extends graphic statics by describing the forces and moments in any 3D rigid-jointed frame structure in terms of cell complexes using homology theory of algebraic topology. Graphic statics provides a highly geometric way to…

Metric Geometry · Mathematics 2026-03-13 Allan McRobie

The $d$-dimensional algebraic connectivity $a_d(G)$ of a graph $G=(V,E)$ is a quantitative measure of its $d$-dimensional rigidity, defined in terms of the eigenvalues of stiffness matrices associated with different embeddings of the graph…

Combinatorics · Mathematics 2025-04-03 Yunseong Jung , Alan Lew

Laman graphs are fundamental to rigidity theory. A graph G with n vertices and m edges is a generic minimally rigid graph (Laman graph), if m=2n-3 and every induced subset of k vertices spans at most 2k-3 edges. We consider the verification…

Combinatorics · Mathematics 2008-01-17 Ovidiu Daescu , Anastasia Kurdia

We study set systems formed by neighborhoods in graphs of bounded twin-width. We start by proving that such graphs have linear neighborhood complexity, in analogy to previous results concerning graphs from classes with bounded expansion and…

Logic in Computer Science · Computer Science 2023-04-27 Wojciech Przybyszewski

In this paper, we study fan-planar drawings that use $h$ layers and are proper, i.e., edges connect adjacent layers. We show that if the embedding of the graph is fixed, then testing the existence of such drawings is fixed-parameter…

We initiate the study of combinatorial algorithms for Triangle Detection in $H$-free graphs. The goal is to decide if a graph that forbids a fixed pattern $H$ as a subgraph contains a triangle, using only "combinatorial" methods that…

Data Structures and Algorithms · Computer Science 2025-11-24 Amir Abboud , Ron Safier , Nathan Wallheimer

We prove that the linear matroid that defines generic rigidity of $d$-dimensional body-rod-bar frameworks (i.e., structures consisting of disjoint bodies and rods mutually linked by bars) can be obtained from the union of ${d+1 \choose 2}$…

Combinatorics · Mathematics 2012-04-26 Shin-ichi Tanigawa

A bar framework determined by a finite graph $G$ and configuration $\bf p$ in $d$ space is universally rigid if it is rigid in any ${\mathbb R}^D \supset {\mathbb R}^d$. We provide a characterization of universally rigidity for any graph…

Metric Geometry · Mathematics 2015-01-29 Robert Connelly , Steven Gortler

A graph $G=(V,E)$ is $d$-sparse if each subset $X\subseteq V$ with $|X|\geq d$ induces at most $d|X|-{{d+1}\choose{2}}$ edges in $G$. Maxwell showed in 1864 that a necessary condition for a generic bar-and-joint framework with at least…

Combinatorics · Mathematics 2022-12-09 Bill Jackson , Hakan Guler

Given a graph $G$, a cost function on the non-edges of $G$, and an integer $d$, the problem of finding a cheapest globally rigid supergraph of $G$ in $\mathbb{R}^d$ is NP-hard for $d\geq 1$. For this problem, which is a common…

Combinatorics · Mathematics 2024-01-19 Tibor Jordán , Soma Villányi