Paper · Nov 8, 2025

Monotonicity of topological entropy along the Ricci flow near a hyperbolic metric

Karen Butt, Alena Erchenko, Tristan Humbert

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Abstract

In 2004, Manning showed that the topological entropy of the geodesic flow of a closed surface of non-constant negative curvature is strictly decreasing along the normalized Ricci flow, and he asked if an analogous result holds in higher dimensions for metrics in a neighborhood of a hyperbolic metric. In this paper, we affirmatively answer this question. Namely, we show that the topological entropy of the geodesic flow of a closed Riemannian manifold that carries a hyperbolic metric is indeed strictly decreasing along the normalized Ricci flow starting from a metric of variable negative sectional curvature sufficiently close to the hyperbolic metric.

Comments: The formula at the bottom of page 11 in v1 is now corrected in v2 (equation (4.13)). The formula for the derivative of the Liouville measure in v1 is corrected in Lemma 3.1. Some propositions were modified and more details provided but the main theorem statements and the overall idea of the proof are unchanged

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  1. Monotonicity of the Liouville entropy along the Ricci flow on surfaces

    Karen Butt, Alena Erchenko, Tristan Humbert et al. PDF

    Topics Ricci flow · Same authors Karen Butt, Alena Erchenko, Tristan Humbert · Shared terms “entropy along”, “constant negative”, “geodesic flow”

  2. Variations of the harmonic entropy and linear drift on negatively curved surfaces

    Karen Butt, Alena Erchenko and Tristan Humbert PDF

    Topics Ricci flow · Same authors Karen Butt, Alena Erchenko, Tristan Humbert · Shared terms “geodesic flow”, “hyperbolic metric”, “strictly decreasing”

  3. A normalized Ricci flow on surfaces with boundary towards the complete hyperbolic metric

    Gang Li PDF

    Topics Ricci flow · Shared terms “hyperbolic metric”, “normalized Ricci”

  4. Minimal surface entropy and applications of Ricci flow on finite-volume hyperbolic 3-manifolds

    Ruojing Jiang and Franco Vargas Pallete PDF

    Topics Ricci flow · Shared terms “hyperbolic metric”, “sectional curvature”

  5. On the stability of Ricci flow on hyperbolic 3-manifolds of finite volume

    Ruojing Jiang and Franco Vargas Pallete PDF

    Topics Ricci flow · Shared terms “hyperbolic metric”, “normalized Ricci”, “sufficiently close”

  6. Convergence stability for Ricci flow on manifolds with bounded geometry

    Eric Bahuaud, Christine Guenther, James Isenberg et al. PDF

    Topics Ricci flow · Shared terms “hyperbolic metric”, “sufficiently close”

  7. Monotonicity of the Cheeger constant under Ricci flow on spheres

    Hollis Williams PDF

    Topics Ricci flow · Shared terms “decreasing along”

  8. Path Connectivity of Anosov Metrics on Surfaces

    Guilherme Brandão Guglielmo and R. Ruggiero PDF

    Topics Ricci flow · Shared terms “geodesic flow”, “negative curvature”, “closed surfaces”

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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. 5A.5
    Uniformization and the Two-Dimensional Ricci FlowBook 5A · Complex Analysis and Conformal Geometry

    Constant-curvature metrics on surfaces, and Ricci flow as a heat equation for the conformal factor.

  2. 10A.12
    Curve Shortening and Minimal DiscsBook 10A · Three-Manifolds and Geometrization

    How loops shrink under curvature, how the discs they bound lose area, and Perelman's extinction estimate.

  3. 11A.1
    The Equation and Its First SolutionsBook 11A · The Ricci Flow: Existence and Maximum Principles

    A heat equation for the metric: spheres, cylinders and scaling.