Connective K-Theory and the Borsuk–Ulam Theorem

  • M. C. CrabbEmail author
Conference paper
Part of the Trends in Mathematics book series (TM)


Let \(k\ge 0\) and \(n,\, r\ge 1\) be natural numbers, and let \(\zeta = \mathrm{e}^{\pi \mathrm{i}/2^k}\). Suppose that \(f : S({\mathbb C}^n) \rightarrow {\mathbb R}^{2r}\) is a continuous map on the unit sphere in \({\mathbb C}^n\) such that, for each \(v\in S({\mathbb C}^n)\), \(f(\zeta v)= - f(v)\). A connective K-theory Borsuk–Ulam theorem is used to show that, if \(n> 2^kr\), then the covering dimension of the space of vectors \(v\in S({\mathbb C}^n)\) such that \(f(v)=0\) is at least \(2(n-2^kr-1)\). It is shown, further, that there exists such a map f for which this zero-set has covering dimension equal to \(2(n-2^kr-1) + 2^{k+2}k+1\).


Borsuk–Ulam theorem Connective K-theory K-theory Euler class 

2010 Mathematics Subject Classification

Primary: 55M25 55N15 55R25 Secondary: 55R40 55R70 55R91 



I am grateful to Prof. Mahender Singh for discussions on some of the material in Sect. 5.


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© Springer Nature Singapore Pte Ltd. 2019

Authors and Affiliations

  1. 1.Institute of Mathematics, University of AberdeenAberdeenUK

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