The spiral index of knots

Colin Adams; William George; Rachel Hudson; Ralph Morrison; Laura Starkston; Samuel Taylor; Olga Turanova

doi:10.1017/s0305004110000241

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arXiv · 0903.0393

The spiral index of knots

Colin Adams·William George·Rachel Hudson·Ralph Morrison·Laura Starkston·Samuel Taylor·Olga Turanova

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Abstract

Two new invariants that are closely related to Milnor's curvature-torsion invariant are introduced. The first, the spiral index of a knot, captures the minimum number of maxima among all knot projections that are free of inflection points. This invariant is closely related to both the bridge and braid index of the knot. The second, the projective superbridge index, provides a method of counting the greatest number of maxima that occur in a given knot projection. In addition to investigating how these invariants are related to the classical invariants, we utilize them to determine all knots with curvature-torsion invariant equal to 6 pi.

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Colin Adams, William George, Rachel Hudson, Ralph Morrison, Laura Starkston, Samuel Taylor, Olga Turanova. 2009-03-03. The spiral index of knots. https://doi.org/10.1017/s0305004110000241

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