Hayden–Sabloff's quasipositivity criterion for exact Lagrangian fillability

A knot is quasipositive if it has the corresponding quasipositive braid or surface representation. Let TB(K)\operatorname{TB}(K) denote the maximal Thurston–Bennequin number of a knot KK, and let PK(v,z)P_K(v,z) denote its HOMFLYPT polynomial. The HOMFLYPT bound is sharp when

TB(K)=maxdegvPK(v,z)1.\operatorname{TB}(K)=-\max\operatorname{deg}_{v}P_K(v,z)-1.

Hayden–Sabloff's conjecture. A knot is exact Lagrangian fillable if and only if it is quasipositive and the HOMFLYPT bound on the maximal Thurston–Bennequin number of KK is sharp.

The source notes that exact Lagrangian fillability implies quasipositivity and sharpness of the HOMFLYPT bound through results on transverse knots, augmentations, rulings, and Legendrian representatives. The converse is stated as a conjecture, with no resolution given here.

Sources & referencesView supporting material

Primary source

Keiji Tagami, “On the Lagrangian fillability of almost positive links”, arXiv:1709.08834 (2023).

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