Paper · May 29, 2023

Classification of compact manifolds with positive isotropic curvature

Hong Huang

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Abstract

We show the following result: Let be a compact manifold of dimension with positive isotropic curvature. Then is diffeomorphic to a spherical space form, or a quotient manifold of by a cocompact discrete subgroup of the isometry group of the round cylinder , or a connected sum of a finite number of such manifolds. This extends previous works of Brendle and Chen-Tang-Zhu, and improves a work of Huang. The proof uses Ricci flow with surgery on compact orbifolds, with the help of the ambient isotopy uniqueness of closed tubular neighborhoods of an isolated singular point in an orbifold.

Comments: 25 pages, restated Lemma 2.1 and Proposition 2.2 and rewrote their proofs

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Connected papers

The 8 papers on this site closest to this one, judged by the topics they share, the words and phrases in their titles and abstracts, and their authors. They are not its citations, but a map of the work around it. Papers here go back to 2021, plus the canon.

Connected papers This paper in the centre and the 8 papers closest to it around it, in date order clockwise from the top. The closer a paper sits to the centre, the stronger the connection. This paper Manifolds with 1/4-pinched Curvature are Space Forms (S. Brendle and R. M. Schoen, 2007)3Brendle 2007 Uniqueness and stability of singular Ricci flows in higher dimensions (Robert Haslhofer, 2021)8Haslhofer 2021 Open manifolds with uniformly positive isotropic curvature (Hong Huang, 2023)1Huang 2023 Rigidity of area non-increasing maps (Man-Chun Lee, Luen-Fai Tam and Jingbo Wan, 2023)7Lee 2023 On Shrinking Ricci solitons with positive isotropic curvature in higher dimensions (Zhengnan Chen, 2025)4Chen 2025 Small Normal Curvature and Three-Manifold Topology (Tsz-Kiu Aaron Chow and Jingbo Wan, 2026)5Chow 2026 Pinching cones for positive isotropic curvature in dimensions seven and eight (Jae Ho Cho, 2026)6Cho 2026 Ricci flow on manifolds with positive isotropic curvature in all dimensions (Simon Brendle and Raphael Tsiamis, 2026)2Brendle 2026
Closer to the centre: more closely connected. Clockwise from the top: oldest to newest. Ricci flowWider flowsalso connected to each other
  1. Open manifolds with uniformly positive isotropic curvature

    Hong Huang PDF

    Topics Surgery, Sphere theorems · Same author Hong Huang · Shared terms “positive isotropic”, “isotropic curvature”, “discrete subgroup”

  2. Ricci flow on manifolds with positive isotropic curvature in all dimensions

    Simon Brendle and Raphael Tsiamis PDF

    Topics Sphere theorems · Shared terms “positive isotropic”, “isotropic curvature”

  3. Manifolds with 1/4-pinched Curvature are Space Forms

    S. Brendle and R. M. SchoenThe canon PDF

    Topics Sphere theorems · Shared terms “positive isotropic”, “isotropic curvature”, “space forms”

  4. On Shrinking Ricci solitons with positive isotropic curvature in higher dimensions

    Zhengnan Chen PDF

    Topics Sphere theorems · Shared terms “positive isotropic”, “isotropic curvature”, “quotient”

  5. Small Normal Curvature and Three-Manifold Topology

    Tsz-Kiu Aaron Chow and Jingbo Wan PDF

    Topics Surgery, Sphere theorems · Shared terms “space forms”, “diffeomorphic”, “Brendle”

  6. Pinching cones for positive isotropic curvature in dimensions seven and eight

    Jae Ho Cho PDF

    Topics Sphere theorems · Shared terms “positive isotropic”, “isotropic curvature”, “compact manifolds”

  7. Rigidity of area non-increasing maps

    Man-Chun Lee, Luen-Fai Tam and Jingbo Wan PDF

    Topics Sphere theorems, Stability & uniqueness · Shared terms “isotropic curvature”, “isometry”, “Brendle”

  8. Uniqueness and stability of singular Ricci flows in higher dimensions

    Robert Haslhofer PDF

    Topics Sphere theorems, Stability & uniqueness · Shared terms “positive isotropic”, “isotropic curvature”, “Chen”

Read around it

Background reading

The guides for the topics of this paper: what each idea is, why it matters, and the papers to read first.

In the guidebook

  1. 11A.11
    Hamilton’s 1982 TheoremBook 11A · The Ricci Flow: Existence and Maximum Principles

    Positive Ricci curvature in dimension 3 flows to a round metric.

  2. 11B.7
    Hamilton’s Program in 2002Book 11B · Solitons, Compactness and Singularities

    What was proved, what was missing, and where Perelman came in.

  3. 12B.5
    The Canonical Neighbourhood TheoremBook 12B · κ-Solutions and Surgery

    Every high-curvature point looks like a neck or a cap.