Paper · Oct 12, 2024

Kähler-Ricci shrinkers and Fano fibrations

Song Sun, Junsheng Zhang

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Abstract

In this paper, we build connections between Kähler-Ricci shrinkers, i.e., complete (possibly non-compact) shrinking gradient Kähler-Ricci solitons, and algebraic geometry. In particular, we (1). prove that a Kähler-Ricci shrinker is naturally a quasi-projective variety, using birational algebraic geometry; (2). formulate a conjecture relating the existence of Kähler-Ricci shrinkers and K-stability of polarized Fano fibrations, which unifies and extends the YTD type conjectures for Kähler-Einstein metrics, Ricci-flat Kähler cone metrics and compact Kähler-Ricci shrinkers; (3). formulate conjectures connecting tangent flows at singularities of Kähler-Ricci flows and algebraic geometry, via a 2-step degeneration for the weighted volume of a Fano fibration.

Comments: v2: minor revisions, with the addition of Proposition 3.10

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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 Uniqueness of asymptotically conical shrinking gradient Kähler-Ricci solitons (Carlos Esparza, 2025)6Esparza 2025 Weak transcendental base-point freeness and diameter lower bounds for the Kähler-Ricci flow (Junsheng Zhang, 2025)5Zhang 2025 K-polystability of Asymptotically Conical Kähler-Ricci Shrinkers (Charles Cifarelli and Carlos Esparza, 2025)8Cifarelli 2025 Singular Kähler–Ricci shrinkers and polarized Fano fibrations (Max Hallgren and Junsheng Zhang, 2026)1Hallgren 2026 Gromov-Hausdorff Limits of Noncollapsed Kähler-Ricci Flows and the Geometry of Ricci Shrinkers (Yu Li and Junsheng Zhang, 2026)3Li 2026 Finite time singularities of the Ricci flow on compact Kähler surfaces are of Type I (Charles Cifarelli, Ronan Conlon, Max Hallgren et al., 2026)7Cifarelli 2026 A Matsushima theorem, uniqueness and K-polystability for Kähler-Ricci shrinkers (Carlos Esparza and Junsheng Zhang, 2026)4Esparza 2026 Scalar curvature bounds and tangent cones for Kähler–Ricci shrinkers (Yu Li and Junsheng Zhang, 2026)2Li 2026
Closer to the centre: more closely connected. Clockwise from the top: oldest to newest. Ricci flowWider flowsalso connected to each other
  1. Singular Kähler–Ricci shrinkers and polarized Fano fibrations

    Max Hallgren and Junsheng Zhang PDF

    Topics Kähler–Ricci flow, Kähler geometry, Ricci solitons · Same author Junsheng Zhang · Shared terms “Fano fibration”, “Ricci shrinkers”, “polarized Fano”

  2. Scalar curvature bounds and tangent cones for Kähler–Ricci shrinkers

    Yu Li and Junsheng Zhang PDF

    Topics Boundaries & non-compact, Kähler geometry, Ricci solitons · Same author Junsheng Zhang · Shared terms “Ricci shrinkers”, “Fano fibration”, “polarized Fano”

  3. Gromov-Hausdorff Limits of Noncollapsed Kähler-Ricci Flows and the Geometry of Ricci Shrinkers

    Yu Li and Junsheng Zhang PDF

    Topics Kähler–Ricci flow, Kähler geometry, Singularities · Same author Junsheng Zhang · Shared terms “Ricci shrinkers”, “Fano fibration”, “Kähler cone”

  4. A Matsushima theorem, uniqueness and K-polystability for Kähler-Ricci shrinkers

    Carlos Esparza and Junsheng Zhang PDF

    Topics Boundaries & non-compact, Kähler geometry, Stability & uniqueness · Same author Junsheng Zhang · Shared terms “Ricci shrinkers”, “Fano fibration”, “polarized Fano”

  5. Weak transcendental base-point freeness and diameter lower bounds for the Kähler-Ricci flow

    Junsheng Zhang PDF

    Topics Kähler–Ricci flow, Kähler geometry, Singularities · Same author Junsheng Zhang · Shared terms “Fano”, “compact Kähler”

  6. Uniqueness of asymptotically conical shrinking gradient Kähler-Ricci solitons

    Carlos Esparza PDF

    Topics Ricci-flat & Calabi–Yau, Kähler–Ricci solitons, Boundaries & non-compact · Shared terms “Fano fibration”, “shrinking gradient”, “gradient Kähler”

  7. Finite time singularities of the Ricci flow on compact Kähler surfaces are of Type I

    Charles Cifarelli, Ronan Conlon, Max Hallgren et al. PDF

    Topics Kähler–Ricci flow, Kähler geometry, Singularities · Same author Junsheng Zhang · Shared terms “compact Kähler”, “tangent flow”

  8. K-polystability of Asymptotically Conical Kähler-Ricci Shrinkers

    Charles Cifarelli and Carlos Esparza PDF

    Topics Boundaries & non-compact, Kähler geometry, Singularities · Shared terms “Ricci shrinkers”, “Fano fibration”, “polarized Fano”

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. 5A.6
    Where This Track LeadsBook 5A · Complex Analysis and Conformal Geometry

    The Kähler–Ricci flow, and when to come back to it.

  2. 11B.4
    Blow-Ups, Blow-Downs and Splitting at InfinityBook 11B · Solitons, Compactness and Singularities

    Limits of rescaled manifolds and flows: why blow-up limits are nonnegatively curved, what blow-downs see, and how lines appear at infinity.

  3. 11B.6
    Rotationally Symmetric Flows and the Standard SolutionBook 11B · Solitons, Compactness and Singularities

    The neckpinch in equations: warped products under the flow, what the maximum principle forces, and the standard solution that surgery glues in.