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math.GT2018
The unbearable hardness of unknotting
Arnaud de Mesmay, Yo'av Rieck, Eric Sedgwick +1
We prove that deciding if a diagram of the unknot can be untangled using at most Riedemeister moves (where is part of the input) is NP-hard. We also prove that several natu…
math.GT2018
On the tree-width of knot diagrams
Arnaud de Mesmay, Jessica Purcell, Saul Schleimer +1
We show that a small tree-decomposition of a knot diagram induces a small sphere-decomposition of the corresponding knot. This, in turn, implies that the knot admits a small essent…