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arXiv · 2201.08466

Obstructing Lagrangian concordance for closures of 3-braids

Angela Wu
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Abstract

We show that any knot which is smoothly the closure of a 3-braid cannot be Lagrangian concordant to and from the maximum Thurston-Bennequin Legendrian unknot except the unknot itself. Our obstruction comes from drawing the Weinstein handlebody diagrams of particular symplectic fillings of cyclic branched double covers of knots in $S^3$. We use the Legendrian contact homology differential graded algebra of the links in these diagrams to compute the symplectic homology of these fillings to derive a contradiction. As a corollary, we find an infinite family of contact manifolds which are rational homology spheres but do not embed in $\mathbb{R}^4$ as contact type hypersurfaces.

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Angela Wu. 2022-01-20. Obstructing Lagrangian concordance for closures of 3-braids. https://arxiv.org/abs/2201.08466

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