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The classic Ky Fan theorem is a combinatorial equivalent of Borsuk-Ulam theorem. It is a generalization and extension of Tucker's lemma and, just like its predecessor, it pinpoints important properties of antipodal colorings of vertices of…

Combinatorics · Mathematics 2024-04-09 Gaiane Panina , Rade Živaljević

We prove multiple generalizations of Fan's combinatorial labeling result for sphere triangulations. This can be seen as a comprehensive extension of the Borsuk--Ulam theorem. In typical applications, the Borsuk--Ulam theorem gives…

Combinatorics · Mathematics 2025-09-10 Florian Frick , Zoe Wellner

We present a constructive proof of Ky Fan's combinatorial lemma concerning labellings of triangulated spheres. Our construction works for triangulations of $S^n$ that contain a flag of hemispheres. As a consequence, we produce a…

Combinatorics · Mathematics 2007-05-23 Timothy Prescott , Francis Edward Su

Tucker and Ky Fan's lemma are combinatorial analogs of the Borsuk-Ulam theorem (BUT). In 1996, Yu. A. Shashkin proved a version of Fan's lemma, which is a combinatorial analog of the odd mapping theorem (OMT). We consider generalizations of…

Combinatorics · Mathematics 2016-10-07 Oleg R. Musin

In this paper some results on the topology of the space of $k$-flats in $\mathbb R^n$ are proved, similar to the Borsuk-Ulam theorem on coverings of sphere. Some corollaries on common transversals for families of compact sets in $\mathbb…

Combinatorics · Mathematics 2011-07-06 R. N. Karasev

We give an essentially self-contained proof of Guth's recent endpoint multilinear Kakeya theorem which avoids the use of somewhat sophisticated algebraic topology, and which instead appeals to the Borsuk-Ulam theorem.

Classical Analysis and ODEs · Mathematics 2012-05-30 Anthony Carbery , Stefan Ingi Valdimarsson

L. Lovasz has shown that Sperner's combinatorial lemma admits a generalization involving a matroid defined on the set of vertices of the associated triangulation. Inspired by this result we prove that classical Ky Fan's theorem admits an…

Combinatorics · Mathematics 2007-10-11 Rade T. Zivaljevic

In combinatorial problems it is sometimes possible to define a $G$-equivariant mapping from a space $X$ of configurations of a system to a Euclidean space $\mathbb{R}^m$ for which a coincidence of the image of this mapping with an…

Algebraic Topology · Mathematics 2008-07-10 Pavle V. M. Blagojevic , Aleksandra S. Dimitrijevic Blagojevic , John McCleary

We observe that the classical Borsuk-Ulam theorem has an easy generalization to maps from an n-manifold M^n to R^n. We point out a geometric corollary.

Algebraic Topology · Mathematics 2007-05-23 Danny Calegari

In this paper we present a Kakutani type theorem that is equivalent to the Borsuk--Ulam theorem for manifolds.

Geometric Topology · Mathematics 2014-11-25 Oleg R. Musin

In this paper we use the strength of the constraint method in combination with a generalized Borsuk-Ulam type theorem and a cohomological intersection lemma to show how one can obtain many new topological transversal theorems of Tverberg…

In this paper we consider several generalizations of the Borsuk-Ulam theorem for G-spaces and apply these results to Tucker type lemmas for G-simplicial complexes and PL-manifolds.

Algebraic Topology · Mathematics 2022-12-27 Oleg R. Musin , Alexey Yu. Volovikov

A generalization of the Borsuk-Ulam theorem to Stiefel manifolds is considered. This theorem is applied to derive bounds on $d$ that guarantee-for a given set of $m$ measures in $\mathbb{R}^d$-the existence of $k$ mutually orthogonal…

Algebraic Topology · Mathematics 2026-05-26 Oleg R. Musin

Tucker's Lemma is a combinatorial analog of the Borsuk-Ulam theorem and the case n=2 was proposed by Tucker in 1945. Numerous generalizations and applications of the Lemma have appeared since then. In 2006 Meunier proved the Lemma in its…

Combinatorics · Mathematics 2009-11-18 Pallavi Jayawant , Peter Wong

We prove an extension of the well-known combinatorial-topological lemma of E. Sperner to the case of infinite-dimensional cubes. It is obtained as a corollary to an infinitary extension of the Lebesgue Covering Dimension Theorem.

General Topology · Mathematics 2007-05-23 Aarno Hohti

This article is concerned with a general scheme on how to obtain constructive proofs for combinatorial theorems that have topological proofs so far. To this end the combinatorial concept of Tucker-property of a finite group $G$ is…

Combinatorics · Mathematics 2007-05-23 Mark de Longueville , Rade T. Zivaljevic

We describe an explicit chain map from the standard resolution to the minimal resolution for the finite cyclic group Z_k of order k. We then demonstrate how such a chain map induces a "Z_k-combinatorial Stokes theorem", which in turn…

Combinatorics · Mathematics 2012-12-27 Bernhard Hanke , Raman Sanyal , Carsten Schultz , Günter M. Ziegler

We use and adapt the Borsuk-Ulam Theorem from topology to derive limitations on list-replicable and globally stable learning algorithms. We further demonstrate the applicability of our methods in combinatorics and topology. We show that,…

Machine Learning · Computer Science 2023-11-06 Zachary Chase , Bogdan Chornomaz , Shay Moran , Amir Yehudayoff

We describe a connective $K$-theory Borsuk--Ulam/Bourgin--Yang theorem for cyclic groups of order a power of a prime $p$. Consider two finite dimensional complex representations $U$ and $V$ of the cyclic group $Z /p^{k+1}$ of order…

Algebraic Topology · Mathematics 2022-11-16 M. C. Crabb

These informal notes, not intended for publication, provide an approach to the Borsuk--Ulam theorem via Stokes' theorem, in a similar spirit to Lima's proof of the Brouwer fixed point theorem. They are intended to be accessible to anyone…

Algebraic Topology · Mathematics 2012-05-22 Anthony Carbery
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