Paper · Mar 29, 2026

A note on the classification of four-dimensional gradient steady and expanding Ricci solitons

Huai-Dong Cao, Junming Xie

PDF Abstract page

As on arXiv

Abstract

In this note, we study the classification of four-dimensional complete gradient steady and expanding Ricci solitons. Specifically, under the asymptotically cylindrical (respectively, asymptotically conical) assumption, we classify gradient steady (respectively, expanding) Ricci solitons with half-harmonic Weyl curvature. In addition, we obtain a partial classification of four-dimensional gradient expanding Ricci solitons with half-nonnegative isotropic curvature.

Comments: 11 pages

Its neighbourhood

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 Curvature estimates for four-dimensional complete gradient expanding Ricci solitons (Huai-Dong Cao and Tianbo Liu, 2021)5Cao 2021 Complete gradient expanding Ricci solitons with finite asymptotic scalar curvature ratio (Huai-Dong Cao, Tianbo Liu and Junming Xie, 2022)6Cao 2022 Four-dimensional complete gradient shrinking Ricci solitons with half positive isotropic curvature (Huai-Dong Cao and Junming Xie, 2022)2Cao 2022 New expanding Ricci solitons starting in dimension four (Jan Nienhaus and Matthias Wink, 2023)8Nienhaus 2023 Four-dimensional gradient Ricci solitons with (half) nonnegative isotropic curvature (Huai-Dong Cao and Junming Xie, 2024)1Cao 2024 Curvature pinching of asymptotically conical gradient expanding Ricci solitons (Huai-Dong Cao and Junming Xie, 2025)4Cao 2025 On curvature estimates for four-dimensional gradient Ricci solitons (Huai-Dong Cao, 2025)3Cao 2025 Kählerity of complete almost-Kähler gradient shrinking Ricci solitons (Junming Xie, 2026)7Xie 2026
Closer to the centre: more closely connected. Clockwise from the top: oldest to newest. Ricci flowWider flowsalso connected to each other
  1. Four-dimensional gradient Ricci solitons with (half) nonnegative isotropic curvature

    Huai-Dong Cao and Junming Xie PDF

    Topics 4-manifolds, Ricci solitons · Same authors Huai-Dong Cao, Junming Xie · Shared terms “dimensional gradient”, “gradient steady”, “nonnegative isotropic”

  2. Four-dimensional complete gradient shrinking Ricci solitons with half positive isotropic curvature

    Huai-Dong Cao and Junming Xie PDF

    Topics 4-manifolds, Boundaries & non-compact, Ricci solitons · Same authors Huai-Dong Cao, Junming Xie · Shared terms “nonnegative isotropic”, “four dimensional”, “half nonnegative”

  3. On curvature estimates for four-dimensional gradient Ricci solitons

    Huai-Dong Cao PDF

    Topics 4-manifolds, Ricci solitons · Same author Huai-Dong Cao · Shared terms “dimensional gradient”, “gradient steady”, “four dimensional”

  4. Curvature pinching of asymptotically conical gradient expanding Ricci solitons

    Huai-Dong Cao and Junming Xie PDF

    Topics 4-manifolds, Boundaries & non-compact, Ricci solitons · Same authors Huai-Dong Cao, Junming Xie · Shared terms “expanding Ricci”, “gradient steady”, “dimensional gradient”

  5. Curvature estimates for four-dimensional complete gradient expanding Ricci solitons

    Huai-Dong Cao and Tianbo Liu PDF

    Topics 4-manifolds, Ricci solitons · Same author Huai-Dong Cao · Shared terms “expanding Ricci”, “four dimensional”, “gradient expanding”

  6. Complete gradient expanding Ricci solitons with finite asymptotic scalar curvature ratio

    Huai-Dong Cao, Tianbo Liu and Junming Xie PDF

    Topics Ricci solitons · Same authors Huai-Dong Cao, Junming Xie · Shared terms “expanding Ricci”, “gradient expanding”, “complete gradient”

  7. Kählerity of complete almost-Kähler gradient shrinking Ricci solitons

    Junming Xie PDF

    Topics 4-manifolds, Boundaries & non-compact, Ricci solitons · Same author Junming Xie · Shared terms “complete gradient”

  8. New expanding Ricci solitons starting in dimension four

    Jan Nienhaus and Matthias Wink PDF

    Topics 4-manifolds, Boundaries & non-compact, Ricci solitons · Shared terms “expanding Ricci”, “gradient expanding”, “asymptotically conical”

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. 11B.1
    Ricci SolitonsBook 11B · Solitons, Compactness and Singularities

    Self-similar solutions: the Gaussian, cylinders, the cigar and the Bryant soliton.

  2. 12B.2
    The Asymptotic Soliton and Three-Dimensional ShrinkersBook 12B · κ-Solutions and Surgery

    Perelman's Proposition 11.2 proved with Morgan and Tian: the reduced-length bounds on κ-solutions, the limit of rescalings, the equality case, and the classification of shrinking solitons in dimensions two and three.