Discrete and Computational Geometry
Let M be a connected, closed, oriented three-manifold and K, L two rationally null-homologous oriented simple closed curves in M. We give an explicit algorithm for computing the linking number between K and L in terms of a presentation of M as an irregular dihedral three-fold cover of S3 branched along a knot α⊂ S3. Since every closed, oriented three-manifold admits such a presentation, our results apply to all (well-defined) linking numbers in all three-manifolds. Furthermore, ribbon obstructions for a knot α can be derived from dihedral covers of α. The linking numbers we compute are necessary for evaluating one such obstruction. This work is a step toward testing potential counter-examples to the Slice-Ribbon Conjecture, among other applications.
3-manifolds, Knots, Linking numbers
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Cahn, Patricia and Kjuchukova, Alexandra, "Linking Numbers in Three-Manifolds" (2021). Mathematics and Statistics: Faculty Publications, Smith College, Northampton, MA.