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Nevo, Santos, and Wilson constructed $2^{\Omega(N^d)}$ combinatorially distinct simplicial $(2d-1)$-spheres with $N$ vertices. We prove that all spheres produced by one of their methods are shellable. Combining this with prior results of…

Combinatorics · Mathematics 2024-05-21 Yirong Yang

We prove that iterated spaces of directions of a limit of a noncollapsing sequence of manifolds with lower curvature bound are topologically spheres. As an application we show that for any finite dimensional Alexandrov space $X^n$ with…

Differential Geometry · Mathematics 2016-09-07 Vitali Kapovitch

In early 1930s Seifert and Threlfall classified up to conjugacy the finite subgroups of $\mathrm{SO}(4)$, this gives an algebraic classification of orientable spherical 3-orbifolds. For the most part, spherical 3-orbifolds are Seifert…

Geometric Topology · Mathematics 2016-07-22 Mattia Mecchia , Andrea Seppi

The critical exponents for a class of one-dimensional models of interface depinning in disordered media can be calculated through a mapping onto directed percolation (DP). In higher dimensions these models give rise to directed surfaces,…

Condensed Matter · Physics 2016-08-16 A. -L. Barabási , G. Grinstein , M. A. Muñoz

A directed space is a topological space $X$ together with a subspace $\vec{P}(X)\subset X^I$ of \emph{directed} paths on $X$. A symmetry of a directed space should therefore respect both the topology of the underlying space and the topology…

Algebraic Topology · Mathematics 2023-06-22 Martin Raussen

For a smooth, closed $n$-manifold $M$, we define an upper semi-continuous integer-valued complexity function on $H^1(M;{\mathbb R})$ using Morse theory. This measures how far an integral class is from being a fiber of a fibration. The fact…

Geometric Topology · Mathematics 2015-06-08 Daryl Cooper , Stephan Tillmann

A classical theorem of Ghouila-Houri from 1960 asserts that every directed graph on $n$ vertices with minimum out-degree and in-degree at least $n/2$ contains a directed Hamilton cycle. In this paper we extend this theorem to a random…

Combinatorics · Mathematics 2014-04-21 Dan Hefetz , Angelika Steger , Benny Sudakov

Let TC$_n$(X) denote the n-th topological complexity of a topological space X. It is known that TC$_n$(X) does not exceed n-1 for non-contractible X, and so it makes sense to describe spaces X with TC$_n$(X) =n-1. Grant--Lupton--Oprea…

Algebraic Topology · Mathematics 2024-08-20 Yuli Rudyak

We give a Morse-theoretic characterization of simple closed geodesics on Riemannian $2$-spheres. On any Riemannian $2$-sphere endowed with a generic metric, we show there exists a simple closed geodesic with Morse index $1$, $2$ and $3$. In…

Differential Geometry · Mathematics 2023-04-13 Dongyeong Ko

The topological complexity TC(X) is a homotopy invariant which reflects the complexity of the problem of constructing a motion planning algorithm in the space X, viewed as configuration space of a mechanical system. In this paper we…

Algebraic Topology · Mathematics 2008-06-26 Michael Farber , Mark Grant

We consider embeddings of a finite complex in a sphere. We give a homotopy theoretic classification of such embeddings in a wide range.

Algebraic Topology · Mathematics 2007-05-23 John R. Klein

Given a Euclidean simplex of dimension $n\geqslant 2$ let its radii of inscribed and circumscribed spheres be $r$ and $R$, and the distance between the centers of the inscribed and circumscribed spheres be $d.$ Then, $(R-nr)(R+(n-2)r)…

Metric Geometry · Mathematics 2023-11-07 Sergei Drozdov

We study the double homology associated to triangulated spheres and present two results. First, we explicitly compute the double homology for minimum degree sphere triangulations. Using a spectral sequence argument, we compute the effect of…

Algebraic Topology · Mathematics 2024-07-02 Carlos Gabriel Valenzuela Ruiz

The degree of a map between orientable manifolds is a fundamental concept in topology, providing deep insights into the structure of manifolds and the behavior of maps between them. Recently, this notion has been extensively studied,…

Geometric Topology · Mathematics 2026-03-24 Biplab Basak , Raju Kumar Gupta , Ayushi Trivedi

We first review some topics in the classical computational geometry of lines, in particular the O(n^{3+\epsilon}) bounds for the combinatorial complexity of the set of lines in R^3 interacting with $n$ objects of fixed description…

Metric Geometry · Mathematics 2007-05-23 Frank Sottile , Thorsten Theobald

We compute the analytic torsion of a cone over a sphere of dimension 1, 2, and 3, and we conjecture a general formula for the cone over an odd dimensional sphere.

Differential Geometry · Mathematics 2012-10-12 L. Hartmann , M. Spreafico

We prove the scalar curvature rigidity for $L^\infty$ metrics on $\mathbb S^n\backslash\Sigma$, where $\mathbb S^n$ is the $n$-dimensional sphere with $n\geq 3$ and $\Sigma$ is a closed subset of $\mathbb S^n$ of codimension at least…

Differential Geometry · Mathematics 2026-05-21 Jinmin Wang , Zhizhang Xie

The shape of homogeneous, generic, smooth convex bodies as described by the Euclidean distance with nondegenerate critical points, measured from the center of mass represents a rather restricted class M_C of Morse-Smale functions on S^2.…

Differential Geometry · Mathematics 2015-12-01 Gábor Domokos , Zsolt Lángi , Tí mea Szabó

We first construct closed spherical CR manifolds of dimension at least five having non-trivial first Chern class with real coefficients. We next prove a constraint on Chern classes with real coefficients of (not necessarily closed)…

Differential Geometry · Mathematics 2022-10-13 Yuya Takeuchi

We describe the topology of singular real algebraic curves in a smooth surface. We enumerate and bound in terms of the degree the number of topological types of singular algebraic curves in the real projective plane.

Algebraic Geometry · Mathematics 2026-01-14 Christopher-Lloyd Simon