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A bar-joint framework $(G,p)$ is the combination of a finite simple graph $G=(V,E)$ and a placement $p:V\rightarrow \mathbb{R}^d$. The framework is rigid if the only edge-length preserving continuous deformations of the vertices arise from…

Combinatorics · Mathematics 2023-12-18 Anthony Nixon , Bernd Schulze , Joseph Wall

We explore the rigidity of generic frameworks in 3-dimensions whose underlying graph is close to being planar. Specifically we consider apex graphs, edge-apex graphs and their variants and prove independence results in the generic…

Combinatorics · Mathematics 2024-02-28 Sean Dewar , Georg Grasegger , Eleftherios Kastis , Anthony Nixon , Brigitte Servatius

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

Rigidity is the property of a structure that does not flex. It is well studied in discrete geometry and mechanics, and has applications in material science, engineering and biological sciences. A bar-and-joint framework is a pair $(G,p)$ of…

Combinatorics · Mathematics 2021-03-02 Sebastian M. Cioabă , Sean Dewar , Xiaofeng Gu

We investigate how to find generic and globally rigid realizations of graphs in $\mathbb{R}^d$ based on elementary geometric observations. Our arguments lead to new proofs of a combinatorial characterization of the global rigidity of graphs…

Combinatorics · Mathematics 2014-08-12 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

The minimal infinitesimal rigidity of bar-joint frameworks in the non-Euclidean spaces (R^2, ||.||_q) are characterised in terms of (2,2)-tight graphs. Specifically, a generically placed bar-joint framework (G,p) in the plane is minimally…

Metric Geometry · Mathematics 2017-05-17 Derek Kitson , Stephen Power

In "Universal rigidity on the line, point orde" it is shown, answering a question of Jord\'an and Nguyen, that universal rigidity of a generic bar-joint framework in R^1 depends on more than the ordering of the vertices. The graph G that…

Metric Geometry · Mathematics 2022-07-19 Bryan Chen , Robert Connelly , Steven J. Gortler , Anthony Nixon , Louis Theran

Recently, Alfakih and Ye [Lin. Algebra Appl. 438:31--36, 2013] proved that if an $r$-dimensional bar framework $(G,p)$ on $n \geq r+2$ nodes in general position in $\R^r$ admits a positive semidefinite stress matrix with rank $n-r-1$, then…

Metric Geometry · Mathematics 2013-05-28 A. Y. Alfakih , Viet-Hang Nguyen

We show that if the joints of a bar and joint framework $(G,p)$ are positioned as `generically' as possible subject to given symmetry constraints and $(G,p)$ possesses a `fully-symmetric' infinitesimal flex (i.e., the velocity vectors of…

Metric Geometry · Mathematics 2009-11-13 Bernd Schulze

We give a combinatorial characterization of generic frameworks that are minimally rigid under the additional constraint of maintaining symmetry with respect to a finite order rotation or a reflection. To establish these results we develop a…

Metric Geometry · Mathematics 2015-03-17 Justin Malestein , Louis Theran

We extend our generic rigidity theory for periodic frameworks in the plane to frameworks with a broader class of crystallographic symmetry. Along the way we introduce a new class of combinatorial matroids and associated linear…

Geometric Topology · Mathematics 2015-03-19 Justin Malestein , Louis Theran

Tanigawa (2016) showed that vertex-redundant rigidity of a graph implies its global rigidity in arbitrary dimension. We extend this result to periodic graphs under fixed lattice representations. A periodic graph is vertex-redundantly rigid…

Metric Geometry · Mathematics 2018-04-24 Viktoria E. Kaszanitzky , Csaba Kiraly , Bernd Schulze

In 1992, Hendrickson proved that (d+1)-connectivity and redundant rigidity are necessary conditions for a generic (non-complete) bar-joint framework to be globally rigid in $\mathbb{R}^d$. Jackson and Jordan confirmed in 2005 that these…

Combinatorics · Mathematics 2019-09-17 Viktoria E. Kaszanitzky , Bernd Schulze , Shin-ichi Tanigawa

A configuration p in r-dimensional Euclidean space is a finite collection of labeled points p^1,p^2,...,p^n in R^r that affinely span R^r. Each configuration p defines a Euclidean distance matrix D_p = (d_ij) = (||p^i-p^j||^2), where ||.||…

Metric Geometry · Mathematics 2012-01-17 A. Y. Alfakih

A rigidity theory is developed for bar-joint frameworks in $\mathbb{R}^{d+1}$ whose vertices are constrained to lie on concentric $d$-spheres with independently variable radii. In particular, combinatorial characterisations are established…

Metric Geometry · Mathematics 2017-02-14 Anthony Nixon , Bernd Schulze , Shin-ichi Tanigawa , Walter Whiteley

We describe a very simple condition that is necessary for the universal rigidity of a complete bipartite framework $(K(n,m),p,q)$. This condition is also sufficient for universal rigidity under a variety of weak assumptions, such as general…

Metric Geometry · Mathematics 2016-10-14 Robert Connelly , Steven J. Gortler

A result due in its various parts to Hendrickson, Connelly, and Jackson and Jord\'an, provides a purely combinatorial characterisation of global rigidity for generic bar-joint frameworks in $\mathbb{R}^2$. The analogous conditions are known…

Metric Geometry · Mathematics 2013-06-12 Bill Jackson , Thomas McCourt , Anthony Nixon

Here it is shown how to combine two generically globally rigid bar frameworks in $d$-space to get another generically globally rigid framework. The construction is to identify $d+1$ vertices from each of the frameworks and erase one of the…

Metric Geometry · Mathematics 2011-03-31 Robert Connelly

In this note we prove a lower bound for the rank of 2-dimensional generic rigidity matroid for regular graphs of degree four and five. Also, we give examples to show the order of the bound we give is sharp.

Combinatorics · Mathematics 2012-07-18 Shisen Luo