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  1. Article

    Open Access

    Trisecting a 4-dimensional book into three chapters

    We describe an algorithm that takes as input an open book decomposition of a closed oriented 4-manifold and outputs an explicit trisection diagram of that 4-manifold. Moreover, a slight variation of this algor...

    Marc Kegel, Felix Schmäschke in Geometriae Dedicata (2024)

  2. No Access

    Article

    Stein traces and characterizing slopes

    We show that there exists an infinite family of pairwise non-isotopic Legendrian knots in the standard contact 3-sphere whose Stein traces are equivalent. This is the first example of such phenomenon. Differen...

    Roger Casals, John Etnyre, Marc Kegel in Mathematische Annalen (2024)

  3. Article

    Open Access

    The Classification of Surfaces via Normal Curves

    We present a simple proof of the surface classification theorem using normal curves. This proof is analogous to Kneser’s and Milnor’s proof of the existence and uniqueness of the prime decomposition of 3-manif...

    Fethi Ayaz, Marc Kegel in Jahresbericht der Deutschen Mathematiker-Vereinigung (2023)

  4. Article

    Open Access

    A Boothby–Wang Theorem for Besse Contact Manifolds

    A Reeb flow on a contact manifold is called Besse if all its orbits are periodic, possibly with different periods. We characterize contact manifolds whose Reeb flows are Besse as principal

    Marc Kegel, Christian Lange in Arnold Mathematical Journal (2021)

  5. No Access

    Article

    Symplectic dynamics and the 3-sphere

    Given a knot in a closed connected orientable 3-manifold we prove that if the exterior of the knot admits an aperiodic contact form that is Euclidean near the boundary, then the 3-manifold is diffeomorphic to ...

    Marc Kegel, Jay Schneider, Kai Zehmisch in Israel Journal of Mathematics (2020)