On the formality of nearly Kähler manifolds and of Joyce's examples in $G_2$-holonomy

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Main Authors: Amann, Manuel, Taimanov, Iskander A.
Format: Preprint
Published: 2020
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_version_ 1866912128017891328
author Amann, Manuel
Taimanov, Iskander A.
author_facet Amann, Manuel
Taimanov, Iskander A.
contents It is a prominent conjecture (relating Riemannian geometry and algebraic topology) that all simply-connected compact manifolds of special holonomy should be formal spaces, i.e., their rational homotopy type should be derivable from their rational cohomology algebra already -- an as prominent as particular property in rational homotopy theory. Special interest now lies on exceptional holonomy $G_2$ and $Spin(7)$. In this article we provide a method of how to confirm that the famous Joyce examples of holonomy $G_2$ indeed are formal spaces; we concretely exert this computation for one example which may serve as a blueprint for the remaining Joyce examples (potentially also of holonomy $Spin(7)$). These considerations are preceded by another result identifying the formality of manifolds admitting special structures: we prove the formality of nearly Kähler manifolds. A connection between these two results can be found in the fact that both "special holonomy" and "nearly Kähler" naturally generalize compact Kähler manifolds, whose formality is a classical and celebrated theorem by Deligne-Griffiths-Morgan-Sullivan.
format Preprint
id arxiv_https___arxiv_org_abs_2012_10915
institution arXiv
publishDate 2020
record_format arxiv
spellingShingle On the formality of nearly Kähler manifolds and of Joyce's examples in $G_2$-holonomy
Amann, Manuel
Taimanov, Iskander A.
Differential Geometry
Algebraic Topology
53C29, 55P62, 57R19, 32Q60 (Primary), 53C26 (Secondary)
It is a prominent conjecture (relating Riemannian geometry and algebraic topology) that all simply-connected compact manifolds of special holonomy should be formal spaces, i.e., their rational homotopy type should be derivable from their rational cohomology algebra already -- an as prominent as particular property in rational homotopy theory. Special interest now lies on exceptional holonomy $G_2$ and $Spin(7)$. In this article we provide a method of how to confirm that the famous Joyce examples of holonomy $G_2$ indeed are formal spaces; we concretely exert this computation for one example which may serve as a blueprint for the remaining Joyce examples (potentially also of holonomy $Spin(7)$). These considerations are preceded by another result identifying the formality of manifolds admitting special structures: we prove the formality of nearly Kähler manifolds. A connection between these two results can be found in the fact that both "special holonomy" and "nearly Kähler" naturally generalize compact Kähler manifolds, whose formality is a classical and celebrated theorem by Deligne-Griffiths-Morgan-Sullivan.
title On the formality of nearly Kähler manifolds and of Joyce's examples in $G_2$-holonomy
topic Differential Geometry
Algebraic Topology
53C29, 55P62, 57R19, 32Q60 (Primary), 53C26 (Secondary)
url https://arxiv.org/abs/2012.10915