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Polyhedra are generically rigid, but can be made to flex under certain symmetry conditions. We generalise Raoul Bricard's 1897 method for making flexible octahedra to construct an infinite family of flexible polyhedra with…

Metric Geometry · Mathematics 2025-10-08 Elvar Atlason , Simon Guest

We study infinitesimal conformal deformations of a triangulated surface in Euclidean space and investigate the change in its extrinsic geometry. A deformation of vertices is conformal if it preserves length cross-ratios. On one hand,…

Metric Geometry · Mathematics 2018-04-19 Wai Yeung Lam , Ulrich Pinkall

We prove that if $G$ is the graph of a connected triangulated $(d-1)$-manifold, for $d\geq 3$, then $G$ is generically globally rigid in $\mathbb R^d$ if and only if it is $(d+1)$-connected and, if $d=3$, $G$ is not planar. The special case…

Combinatorics · Mathematics 2024-09-26 James Cruickshank , Bill Jackson , Shin-ichi Tanigawa

In this paper we prove the scalar curvature extremality and rigidity for a class of warped product spaces that are possibly degenerate at the two ends. The leaves of these warped product spaces can be any closed Riemannian manifolds with…

Differential Geometry · Mathematics 2023-12-19 Jinmin Wang , Zhizhang Xie

It is known that the space of convex polygons in the Euclidean plane with fixed normals, up to homotheties and translations, endowed with the area form, is isometric to a hyperbolic polyhedron. In this note we show a class of convex…

Differential Geometry · Mathematics 2013-04-05 François Fillastre

A family of closed manifolds is called cohomologically rigid if a cohomology ring isomorphism implies a diffeomorphism for any two manifolds in the family. We establish cohomological rigidity for large families of 3-dimensional and…

Algebraic Topology · Mathematics 2017-07-25 Victor Buchstaber , Nikolay Erokhovets , Mikiya Masuda , Taras Panov , Seonjeong Park

A very fundamental geometric problem on finite systems of spheres was independently phrased by Kneser (1955) and Poulsen (1954). According to their well-known conjecture if a finite set of balls in Euclidean space is repositioned so that…

Metric Geometry · Mathematics 2011-09-29 Karoly Bezdek

Identifying parallel sides of a collection of Euclidean polygons yields a flat surface with cone points of angles multiples of 2 pi, naturally a compact Riemann surface but also an algebraic curve, and a hyperbolic surface. In general two…

Geometric Topology · Mathematics 2007-06-13 Samuel Lelièvre , Robert Silhol

We consider 3-dimensional hyperbolic cone-manifolds, singular along infinite lines, which are ``convex co-compact'' in a natural sense. We prove an infinitesimal rigidity statement when the angle around the singular lines is less than…

Differential Geometry · Mathematics 2014-02-12 Sergiu Moroianu , Jean-Marc Schlenker

In an Euclidean $d$-space, the container problem asks to pack $n$ equally sized spheres into a minimal dilate of a fixed container. If the container is a smooth convex body and $d\geq 2$ we show that solutions to the container problem can…

Metric Geometry · Mathematics 2011-10-20 Achill Schuermann

Let M be a translation surface. We show that certain deformations of M supported on the set of all cylinders in a given direction remain in the GL(2,R)-orbit closure of M. Applications are given concerning complete periodicity, field of…

Dynamical Systems · Mathematics 2016-01-20 Alex Wright

A topological commutative ring is said to be rigid when for every set $X$, the topological dual of the $X$-fold topological product of the ring is isomorphic to the free module over $X$. Examples are fields with a ring topology, discrete…

Commutative Algebra · Mathematics 2018-08-21 Laurent Poinsot

This paper gives a partial confirmation of a conjecture of P. Agarwal, S. Har-Peled, M. Sharir, and K. Varadarajan that the total curvature of a shortest path on the boundary of a convex polyhedron in the 3-dimensional Euclidean space…

Metric Geometry · Mathematics 2007-05-23 Imre Barany , Krystyna Kuperberg , Tudor Zamfirescu

It is shown that every accessible group which is integrable orbit equivalent to a free group is virtually free. Moreover, we also show that any integrable orbit-equivalence between finitely generated groups extends to their end…

Dynamical Systems · Mathematics 2016-01-05 Lewis Bowen

We prove that on the twisted cotangent bundle of a closed manifold with an exact magnetic form, a Hamiltonian system of a time-dependent Tonelli Hamiltonian function possesses infinitely many brake orbits. More precisely, by applying…

Dynamical Systems · Mathematics 2023-02-21 Duanzhi Zhang , Zhihao Zhao

In this paper, we combine separate works on (a) the transfer of infinitesimal rigidity results from an Euclidean space to the next higher dimension by coning, (b) the further transfer of these results to spherical space via associated…

Metric Geometry · Mathematics 2011-08-11 Bernd Schulze , Walter Whiteley

The triangulation complexity of a closed orientable 3-manifold is the minimal number of tetrahedra in any triangulation of the manifold. The main theorem of the paper gives upper and lower bounds on the triangulation complexity of any…

Geometric Topology · Mathematics 2024-07-24 Marc Lackenby , Jessica S. Purcell

Haag, Kertzer, Rickards, and Stange disprove the Local-Global Conjecture for Apollonian circle packings. We extend their disproof to four more types of integral circle packing: the octahedral, cubic, square, and triangular packings. In each…

Number Theory · Mathematics 2026-03-27 Hanqi Shi , Wenyuan Shi , Ian Whitehead , Ham Williams-Tracy , Jeffrey Zhirui Zhang

Here we propose a class of frameworks in the plane, braced polygons, that may be globally rigid and are analogous to convex polyopes in 3 space that are rigid by Cauchy's rigidity Theorem in 1813.

Metric Geometry · Mathematics 2024-10-10 Robert Connelly , Bill Jackson , Shin-ichi Tanigawa , Zhen Zhang

In this article, we generalize Eberlein's Rigidity Theorem to the singular case, namely, one of the spaces is only assumed to be a CAT(0) topological manifold. As a corollary, we get that any compact irreducible but locally reducible…

Geometric Topology · Mathematics 2007-05-23 Michael W. Davis , Boris Okun , Fangyang Zheng