Paper · Mar 30, 2026

Ancient Ricci flows with nonnegative Ricci curvature

Yuxing Deng, Ganqi Wang, Yongjia Zhang

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Abstract

In this paper, we study the asymptotic geometry of a noncollapsed ancient Ricci flow with nonnegative Ricci curvature via its tangent flow at infinity – a noncollapsed -limit metric soliton [Bam23,CMZ23]. We first prove some estimates for noncollapsed -limit metric solitons with nonnegative Ricci curvature, and then obtain two dichotomy theorems for ancient Ricci flows. In particular, we show that: (1) for a noncollapsed ancient Ricci flow with nonnegative Ricci curvature, either its asymptotic volume ratio is always zero, or every tangent flow at infinity is a Ricci flat cone; (2) for a noncollapsed ancient Ricci flow with positively pinched Ricci curvature (), either it is compact, or every tangent flow at infinity is a Ricci flat cone.

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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 On Ricci flows with closed and smooth tangent flows (Pak-Yeung Chan, Zilu Ma and Yongjia Zhang, 2021)3Chan 2021 On the fundamental group of non-collapsed ancient Ricci flows (Richard H. Bamler, 2021)4Bamler 2021 An optimal volume growth estimate for noncollapsed steady gradient Ricci solitons (Richard H. Bamler, Pak-Yeung Chan, Zilu Ma et al., 2021)7Bamler 2021 Dimension Reduction for Positively Curved Steady Solitons (Pak-Yeung Chan, Zilu Ma and Yongjia Zhang, 2023)5Chan 2023 On noncollapsed F-limit metric solitons (Pak-Yeung Chan, Zilu Ma and Yongjia Zhang, 2024)2Chan 2024 On the fundamental group of steady gradient Ricci solitons with nonnegative sectional curvature (Yuxing Deng and Yuehan Hao, 2024)8Deng 2024 Rigidity of positively curved Steady gradient Ricci solitons on orbifolds (Yuxing Deng, 2025)6Deng 2025 A gap theorem for metric solitons and its applications (Ganqi Wang and Yongjia Zhang, 2026)1Wang 2026
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  1. A gap theorem for metric solitons and its applications

    Ganqi Wang and Yongjia Zhang PDF

    Topics Ancient solutions, Singularities · Same authors Ganqi Wang, Yongjia Zhang · Shared terms “limit metric”, “volume ratio”, “asymptotic volume”

  2. On noncollapsed -limit metric solitons

    Pak-Yeung Chan, Zilu Ma and Yongjia Zhang PDF

    Topics (Non)collapsing, Singularities · Same author Yongjia Zhang · Shared terms “limit metric”, “noncollapsed”

  3. On Ricci flows with closed and smooth tangent flows

    Pak-Yeung Chan, Zilu Ma and Yongjia Zhang PDF

    Topics Ancient solutions, Singularities · Same author Yongjia Zhang · Shared terms “tangent flow”, “dichotomy theorem”

  4. On the fundamental group of non-collapsed ancient Ricci flows

    Richard H. Bamler PDF

    Topics (Non)collapsing, Ancient solutions, Singularities · Shared terms “tangent flow”

  5. Dimension Reduction for Positively Curved Steady Solitons

    Pak-Yeung Chan, Zilu Ma and Yongjia Zhang PDF

    Topics (Non)collapsing, Singularities · Same author Yongjia Zhang · Shared terms “noncollapsed”, “positively”, “tangent flow”

  6. Rigidity of positively curved Steady gradient Ricci solitons on orbifolds

    Yuxing Deng PDF

    Topics (Non)collapsing, Ancient solutions, Singularities · Same author Yuxing Deng · Shared terms “positively”, “noncollapsed”

  7. An optimal volume growth estimate for noncollapsed steady gradient Ricci solitons

    Richard H. Bamler, Pak-Yeung Chan, Zilu Ma et al. PDF

    Topics (Non)collapsing, Ancient solutions · Same author Yongjia Zhang · Shared terms “noncollapsed”

  8. On the fundamental group of steady gradient Ricci solitons with nonnegative sectional curvature

    Yuxing Deng and Yuehan Hao PDF

    Topics (Non)collapsing · Same author Yuxing Deng · Shared terms “noncollapsed”

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Background reading

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In the guidebook

  1. 12B.4
    Compactness and Universal Estimates for κ-SolutionsBook 12B · κ-Solutions and Surgery

    Asymptotic volume zero, curvature controlled by volume, Perelman's Theorem 11.7, a universal κ, neck-like behaviour at infinity, and the constants that canonical neighbourhoods inherit.

  2. 12B.3
    The Structure of κ-SolutionsBook 12B · κ-Solutions and Surgery

    Necks and caps, compactness, and universal estimates.

  3. 9B.3
    Collapsing and NoncollapsingBook 9B · Comparison, Convergence and Heat on Manifolds

    Injectivity radius bounds from volume, collapsing examples, and the definition Perelman needs.