Free torus actions and twisted suspensions

We express the total space of a principal circle bundle over a connected sum of two manifolds in terms of the total spaces of circle bundles over each summand, provided certain conditions hold. We then apply this result to provide sufficient conditions for the existence of free circle and torus acti...

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Main Authors: Fernando Galaz-García, Philipp Reiser
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/S2050509424001415/type/journal_article
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author Fernando Galaz-García
Philipp Reiser
author_facet Fernando Galaz-García
Philipp Reiser
author_sort Fernando Galaz-García
collection DOAJ
description We express the total space of a principal circle bundle over a connected sum of two manifolds in terms of the total spaces of circle bundles over each summand, provided certain conditions hold. We then apply this result to provide sufficient conditions for the existence of free circle and torus actions on connected sums of products of spheres and obtain a topological classification of closed, simply connected manifolds with a free cohomogeneity-four torus action. As a corollary, we obtain infinitely many manifolds with Riemannian metrics of positive Ricci curvature and isometric torus actions.
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series Forum of Mathematics, Sigma
spelling doaj-art-5f1fc85ed4974178b7d7e3663b015e072025-01-20T06:07:59ZengCambridge University PressForum of Mathematics, Sigma2050-50942025-01-011310.1017/fms.2024.141Free torus actions and twisted suspensionsFernando Galaz-García0https://orcid.org/0000-0003-3428-5190Philipp Reiser1https://orcid.org/0000-0002-7997-7484Department of Mathematical Sciences, Durham University, Upper Mountjoy Campus, Stockton Rd, Durham DH1 3LE, United Kingdom; E-mail: .Department of Mathematics, University of Fribourg, Chem. du Musée 23, 1700 Fribourg, SwitzerlandWe express the total space of a principal circle bundle over a connected sum of two manifolds in terms of the total spaces of circle bundles over each summand, provided certain conditions hold. We then apply this result to provide sufficient conditions for the existence of free circle and torus actions on connected sums of products of spheres and obtain a topological classification of closed, simply connected manifolds with a free cohomogeneity-four torus action. As a corollary, we obtain infinitely many manifolds with Riemannian metrics of positive Ricci curvature and isometric torus actions.https://www.cambridge.org/core/product/identifier/S2050509424001415/type/journal_article57S1555R1553C2057R6557R2255R25
spellingShingle Fernando Galaz-García
Philipp Reiser
Free torus actions and twisted suspensions
Forum of Mathematics, Sigma
57S15
55R15
53C20
57R65
57R22
55R25
title Free torus actions and twisted suspensions
title_full Free torus actions and twisted suspensions
title_fullStr Free torus actions and twisted suspensions
title_full_unstemmed Free torus actions and twisted suspensions
title_short Free torus actions and twisted suspensions
title_sort free torus actions and twisted suspensions
topic 57S15
55R15
53C20
57R65
57R22
55R25
url https://www.cambridge.org/core/product/identifier/S2050509424001415/type/journal_article
work_keys_str_mv AT fernandogalazgarcia freetorusactionsandtwistedsuspensions
AT philippreiser freetorusactionsandtwistedsuspensions