Paper · Jul 30, 2024

Topological Obstructions to the Existence of Compact Shrinking Ricci Solitons in Dimension Four

Cameron MacMahon

As on arXiv

Abstract

This undergraduate thesis is focused on introducing the reader to concepts related to the search for topological obstructions to the existence of compact gradient shrinking Ricci soliton metrics in dimension four. It contains a discussion of the relevant background material for this subject. Furthermore, it introduces the problem of extending the Hitchin-Thorpe inequality to gradient shrinking Ricci soliton metrics and explores the limitations of current results in that direction. At last, the topic of compact Kaehler gradient shrinking Ricci solitons is introduced and the classification of these spaces is outlined in literature-study fashion.

Submitted
Jul 30, 2024
Last revised
Jul 24, 2026 (v3)
Subjects
math.DG

Comments: 18 pages, Undergraduate Thesis. This is a second version. The Author was not aware of reference 1, which proved theorem 4.4 independently of Cao, to whom the theorem was credited in version 1. See also the "Editor's Note" for some corrections to Section 5, contributed by Brian Klatt, for which the author is grateful

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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 Euler characteristic and Hitchin-Thorpe inequality for four-dimensional compact Ricci solitons (Xu Cheng, Ernani Ribeiro and Detang Zhou, 2022)1Cheng 2022 Vanishing bach-like tensors on complete gradient shrinking ricci solitons (James Siene, 2023)5Siene 2023 Geometry and Analysis of Gradient Ricci Solitons in Dimension Four (Xiaodong Cao and Hung Tran, 2024)4Cao 2024 Gradient Shrinking Ricci Solitons and Modified Sectional Curvature (Xiaodong Cao, Ernani Ribeiro and Hosea Wondo, 2025)2Cao 2025 On curvature estimates for four-dimensional gradient Ricci solitons (Huai-Dong Cao, 2025)8Cao 2025 Rigidity of Gradient Shrinking Ricci Solitons with a Vanishing Bach-like Tensor and Related Variational Formulas (James Siene, 2025)6Siene 2025 Diameter estimates and Hitchin-Thorpe inequality for four-dimensional compact Quasi-Einstein manifolds (Samuel Belo, 2026)7Belo 2026 Kählerity of complete almost-Kähler gradient shrinking Ricci solitons (Junming Xie, 2026)3Xie 2026
Closer to the centre: more closely connected. Clockwise from the top: oldest to newest. Ricci flowWider flowsalso connected to each other
  1. On Euler characteristic and Hitchin-Thorpe inequality for four-dimensional compact Ricci solitons

    Xu Cheng, Ernani Ribeiro and Detang Zhou

    Topics 4-manifolds, Ricci solitons · Shared terms “Thorpe inequality”, “Hitchin Thorpe”, “compact gradient”

  2. Gradient Shrinking Ricci Solitons and Modified Sectional Curvature

    Xiaodong Cao, Ernani Ribeiro and Hosea Wondo

    Topics 4-manifolds, Kähler geometry, Ricci solitons · Shared terms “shrinking Ricci”, “gradient shrinking”, “Hitchin Thorpe”

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

    Junming Xie

    Topics 4-manifolds, Kähler geometry, Ricci solitons · Shared terms “shrinking Ricci”, “gradient shrinking”, “dimension four”

  4. Geometry and Analysis of Gradient Ricci Solitons in Dimension Four

    Xiaodong Cao and Hung Tran

    Topics 4-manifolds, Ricci solitons · Shared terms “dimension four”

  5. Vanishing bach-like tensors on complete gradient shrinking ricci solitons

    James Siene

    Topics 4-manifolds, Ricci solitons · Shared terms “shrinking Ricci”, “gradient shrinking”

  6. Rigidity of Gradient Shrinking Ricci Solitons with a Vanishing Bach-like Tensor and Related Variational Formulas

    James Siene

    Topics 4-manifolds, Ricci solitons · Shared terms “shrinking Ricci”, “gradient shrinking”, “extending”

  7. Diameter estimates and Hitchin-Thorpe inequality for four-dimensional compact Quasi-Einstein manifolds

    Samuel Belo

    Topics 4-manifolds, Ricci solitons · Shared terms “Thorpe inequality”, “Hitchin Thorpe”, “dimension four”

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.