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JOURNALS // Symmetry, Integrability and Geometry: Methods and Applications // Archive

SIGMA, 2024 Volume 20, 109, 13 pp. (Mi sigma2111)

Lagrangian Surplusection Phenomena

Georgios Dimitroglou Rizella, Jonathan David Evansb

a Department of Mathematics, Uppsala Universitet, Uppsala, Sweden
b Department of Mathematics and Statistics, Lancaster University, Bailrigg, UK

Abstract: Suppose you have a family of Lagrangian submanifolds $L_t$ and an auxiliary Lagrangian $K$. Suppose that $K$ intersects some of the $L_t$ more than the minimal number of times. Can you eliminate surplus intersection (surplusection) with all fibres by performing a Hamiltonian isotopy of $K$? Or will any Lagrangian isotopic to $K$ surplusect some of the fibres? We argue that in several important situations, surplusection cannot be eliminated, and that a better understanding of surplusection phenomena (better bounds and a clearer understanding of how the surplusection is distributed in the family) would help to tackle some outstanding problems in different areas, including Oh's conjecture on the volume-minimising property of the Clifford torus and the concurrent normals conjecture in convex geometry. We pose many open questions.

Keywords: symplectic geometry, Lagrangian intersections, Floer theory.

MSC: 53D12, 53D40

Received: September 3, 2024; in final form November 23, 2024; Published online December 6, 2024

Language: English

DOI: 10.3842/SIGMA.2024.109


ArXiv: 2408.14883


© Steklov Math. Inst. of RAS, 2025