New York Journal of Mathematics
Volume 18 (2012) 389-408


Chan-Ho Suh

Boundary-twisted normal form and the number of elementary moves to unknot

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Published: June 4, 2012
Keywords: Reidemeister move, unknotting, normal surface
Subject: Primary 57M, 57N10; Secondary 68Q25

Suppose K is an unknot lying in the 1-skeleton of a triangulated 3-manifold with t tetrahedra. Hass and Lagarias showed there is an upper bound, depending only on t, for the minimal number of elementary moves to untangle K. We give a simpler proof, utilizing a normal form for surfaces whose boundary is contained in the 1-skeleton of a triangulated 3-manifold. We also obtain a significantly better upper bound of 2120t+14 and improve the Hass-Lagarias upper bound on the number of Reidemeister moves needed to unknot to 2105 n, where n is the crossing number.


Research was partially funded by the National Science Foundation (VIGRE DMS-0135345 and DMS-0636297).

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University of California, One Shields Avenue, Davis, CA 95616