Two-bridge knot transvergent diagram conjecture

Let KK be a two-bridge knot, written in Conway notation as C(a1,,an)C(a_1,\ldots,a_n). A transvergent diagram is a diagram with the relevant transverse symmetry, and let c(K)c(K) denote the crossing number of KK. The conditions are: either nn is even, all ai>0a_i>0, and a2,a4,a_2,a_4,\ldots are even; or nn is odd, all ai>0a_i>0, and the twist-numbers are symmetric, so that a1=ana_1=a_n, a2=an1a_2=a_{n-1}, and so on. In the latter case, an+12a_{\frac{n+1}{2}} is necessarily odd.

Two-bridge knot transvergent diagram conjecture. A two-bridge knot KK has a transvergent diagram with c(K)c(K) crossings if and only if one of these two conditions is fulfilled.

This conjecture characterizes when the minimal crossing number can be realized by a transvergent diagram. It is illustrated for two-bridge knots with crossing number less than 88; the source provides no resolution of the general claim.

Sources & referencesView supporting material

Primary source

Christoph Lamm, “Symmetric diagrams for all strongly invertible knots up to 10 crossings”, arXiv:2210.13198 (2025).

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