Paper · Mar 23, 2026

PIC1 pinched manifolds are flat or compact

Alix Deruelle, Man-Chun Lee, Felix Schulze, Miles Simon, Peter M. Topping

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Abstract

Hamilton's pinching conjecture, that three-dimensional complete non-compact manifolds with pinched Ricci curvature are flat, has recently been resolved using Ricci flow. In this paper we prove a direct analogue of that result in all dimensions. In order to do so we develop a lifting technique that allows us to handle manifolds that are collapsed at infinity. This new method also gives an alternative way of handling collapsed manifolds in the known three-dimensional case. As part of this approach, we prove a Ricci flow curvature estimate of a type that would normally be derived from the Harnack inequality, but without requiring the strong curvature positivity hypothesis demanded by Harnack. We give an improved gap theorem as a further application.

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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 Initial stability estimates for Ricci flow and three dimensional Ricci-pinched manifolds (Alix Deruelle, Felix Schulze and Miles Simon, 2022)3Deruelle 2022 Three-manifolds with non-negatively pinched Ricci curvature (Man-Chun Lee and Peter M. Topping, 2022)2Lee 2022 Manifolds with PIC1 pinched curvature (Man-Chun Lee and Peter M. Topping, 2022)1Lee 2022 Gap Theorem on Riemannian manifolds using Ricci flow (Pak-Yeung Chan and Man-Chun Lee, 2023)8Chan 2023 Ricci flow and PIC1 (Peter M. Topping, 2023)5Topping 2023 On the Hamilton-Lott conjecture in higher dimensions (Alix Deruelle, Felix Schulze and Miles Simon, 2024)4Deruelle 2024 The Harnack inequality without convexity for curve shortening flow (Arjun Sobnack and Peter M. Topping, 2026)7Sobnack 2026 Spaces with distributional scalar curvature bounded from below: Optimal regularity and positive mass (Man-Chun Lee, Florian Litzinger and Miles Simon, 2026)6Lee 2026
Closer to the centre: more closely connected. Clockwise from the top: oldest to newest. Ricci flowWider flowsalso connected to each other
  1. Manifolds with PIC1 pinched curvature

    Man-Chun Lee and Peter M. Topping PDF

    Topics Sphere theorems, 3-manifolds, Boundaries & non-compact · Same authors Man-Chun Lee, Peter M. Topping · Shared terms “PIC pinched”, “pinched Ricci”, “dimensional complete”

  2. Three-manifolds with non-negatively pinched Ricci curvature

    Man-Chun Lee and Peter M. Topping PDF

    Topics Curvature pinching, 3-manifolds, Boundaries & non-compact · Same authors Man-Chun Lee, Peter M. Topping · Shared terms “pinched Ricci”, “pinching conjecture”, “Hamilton pinching”

  3. Initial stability estimates for Ricci flow and three dimensional Ricci-pinched manifolds

    Alix Deruelle, Felix Schulze and Miles Simon PDF

    Topics 3-manifolds · Same authors Alix Deruelle, Felix Schulze, Miles Simon · Shared terms “pinched manifold”, “Hamilton”

  4. On the Hamilton-Lott conjecture in higher dimensions

    Alix Deruelle, Felix Schulze and Miles Simon PDF

    Topics Sphere theorems, Boundaries & non-compact · Same authors Alix Deruelle, Felix Schulze, Miles Simon · Shared terms “PIC”, “dimensional complete”, “Hamilton”

  5. Ricci flow and PIC1

    Peter M. Topping PDF

    Topics Sphere theorems · Same author Peter M. Topping · Shared terms “PIC”

  6. The Harnack inequality without convexity for curve shortening flow

    Arjun Sobnack and Peter M. ToppingWider flows PDF

    Topics Harnack inequalities · Same author Peter M. Topping · Shared terms “curvature estimates”, “alternative”, “Hamilton”

  7. Gap Theorem on Riemannian manifolds using Ricci flow

    Pak-Yeung Chan and Man-Chun Lee PDF

    Topics 3-manifolds, Boundaries & non-compact · Same author Man-Chun Lee · Shared terms “gap theorem”, “curvature estimates”

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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.7
    Maximum Principles under Ricci FlowBook 11A · The Ricci Flow: Existence and Maximum Principles

    Scalar and tensor maximum principles, and preserved curvature conditions.

  2. 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.

  3. 6D.5
    Diffusions on Manifolds and CurvatureBook 6D · Diffusions, Finance and Computation

    Brownian motion on a Riemannian manifold, the Bakry–Émery calculus, curvature-dimension inequalities, gradient estimates and log-Sobolev, coupling, and Brownian motion along a Ricci flow.