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arXiv · 2506.15111

The Legendrian Hopf Link has exactly two Lagrangian fillings

Bryce Thomson
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Abstract

We prove that there are precisely two embedded exact Lagrangian fillings of the standard Legendrian Hopf link, up to compactly supported Hamiltonian isotopy. It was known that the standard Legendrian Hopf link admitted at least two such Lagrangian fillings: we show these are all. Specifically, we use a type of neck-stretching procedure to construct a pseudoholomorphic conic fibration that makes a given arbitrary exact Lagrangian filling fiber over a real curve, under a global pseudoholomorphic Lefschetz fibration. This then allows for an explicit Hamiltonian isotopy to be constructed from any given Lagrangian filling to one of two known standard fillings.

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Bryce Thomson. 2026-09-22. The Legendrian Hopf Link has exactly two Lagrangian fillings. https://arxiv.org/abs/2506.15111

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