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Cobordism distance on the projective space of the knot concordance group

Published online by Cambridge University Press:  27 June 2023

Charles Livingston*
Affiliation:
Department of Mathematics, Indiana University, Bloomington, IN 47405, USA

Abstract

We use the cobordism distance on the smooth knot concordance group $\mathcal {C}$ to measure how close two knots are to being linearly dependent. Our measure, $\Delta (\mathcal {K}, \mathcal {J})$, is built by minimizing the cobordism distance between all pairs of knots, $\mathcal {K}'$ and $\mathcal {J}'$, in cyclic subgroups containing $\mathcal {K}$ and $\mathcal {J}$. When made precise, this leads to the definition of the projective space of the concordance group, ${\mathbb P}(\mathcal {C})$, upon which $\Delta $ defines an integer-valued metric. We explore basic properties of ${\mathbb P}(\mathcal {C})$ by using torus knots $T_{2,2k+1}$. Twist knots are used to demonstrate that the natural simplicial complex $\overline {({\mathbb P}(\mathcal {C}), \Delta )}$ associated with the metric space ${\mathbb P}(\mathcal {C})$ is infinite-dimensional.

Type
Article
Copyright
© The Author(s), 2023. Published by Cambridge University Press on behalf of The Canadian Mathematical Society

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Footnotes

This work was supported by a grant from the National Science Foundation (Grant No. NSF-DMS-1505586).

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