Graphing, homotopy groups of spheres, and spaces of long links and knots

We study homotopy groups of spaces of long links in Euclidean space of codimension at least three. With multiple components, they admit split injections from homotopy groups of spheres. We show that, up to knotting, these account for all the homotopy groups in a range which depends on the dimensions...

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Main Author: Robin Koytcheff
Format: Article
Language:English
Published: Cambridge University Press 2025-01-01
Series:Forum of Mathematics, Sigma
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Online Access:https://www.cambridge.org/core/product/identifier/S2050509424001142/type/journal_article
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author Robin Koytcheff
author_facet Robin Koytcheff
author_sort Robin Koytcheff
collection DOAJ
description We study homotopy groups of spaces of long links in Euclidean space of codimension at least three. With multiple components, they admit split injections from homotopy groups of spheres. We show that, up to knotting, these account for all the homotopy groups in a range which depends on the dimensions of the source manifolds and target manifold and which roughly generalizes the triple-point-free range for isotopy classes. Just beyond this range, joining components sends both a parametrized long Borromean rings class and a Hopf fibration to a generator of the first nontrivial homotopy group of the space of long knots. For spaces of equidimensional long links of most source dimensions, we describe generators for the homotopy group in this degree in terms of these Borromean rings and homotopy groups of spheres. A key ingredient in most of our results is a graphing map which increases source and target dimensions by one.
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spelling doaj-art-c08c39157e0043c0a17d67941101c7622025-02-12T03:49:18ZengCambridge University PressForum of Mathematics, Sigma2050-50942025-01-011310.1017/fms.2024.114Graphing, homotopy groups of spheres, and spaces of long links and knotsRobin Koytcheff0https://orcid.org/0000-0002-1056-5318Department of Mathematics, University of Louisiana at Lafayette, Lafayette, 70504 LA, USAWe study homotopy groups of spaces of long links in Euclidean space of codimension at least three. With multiple components, they admit split injections from homotopy groups of spheres. We show that, up to knotting, these account for all the homotopy groups in a range which depends on the dimensions of the source manifolds and target manifold and which roughly generalizes the triple-point-free range for isotopy classes. Just beyond this range, joining components sends both a parametrized long Borromean rings class and a Hopf fibration to a generator of the first nontrivial homotopy group of the space of long knots. For spaces of equidimensional long links of most source dimensions, we describe generators for the homotopy group in this degree in terms of these Borromean rings and homotopy groups of spheres. A key ingredient in most of our results is a graphing map which increases source and target dimensions by one.https://www.cambridge.org/core/product/identifier/S2050509424001142/type/journal_article57K4555Q4057R4055R8058D1081Q3055P35
spellingShingle Robin Koytcheff
Graphing, homotopy groups of spheres, and spaces of long links and knots
Forum of Mathematics, Sigma
57K45
55Q40
57R40
55R80
58D10
81Q30
55P35
title Graphing, homotopy groups of spheres, and spaces of long links and knots
title_full Graphing, homotopy groups of spheres, and spaces of long links and knots
title_fullStr Graphing, homotopy groups of spheres, and spaces of long links and knots
title_full_unstemmed Graphing, homotopy groups of spheres, and spaces of long links and knots
title_short Graphing, homotopy groups of spheres, and spaces of long links and knots
title_sort graphing homotopy groups of spheres and spaces of long links and knots
topic 57K45
55Q40
57R40
55R80
58D10
81Q30
55P35
url https://www.cambridge.org/core/product/identifier/S2050509424001142/type/journal_article
work_keys_str_mv AT robinkoytcheff graphinghomotopygroupsofspheresandspacesoflonglinksandknots