Knot adjacency, genus and essential tori

• Autores: Efstratia Kalfagianni, Xiaobiao Lin
• Localización: Pacific journal of mathematics, ISSN 0030-8730, Vol. 228, Nº 2, 2006, págs. 251-276
• Idioma: inglés
• DOI: 10.2140/pjm.2006.228.251
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• Resumen

  • A knot K is called n-adjacent to another knot K' if K admits a projection containing n generalized crossings such that changing any 0 < m = n of them yields a projection of K'. We apply techniques from the theory of sutured 3-manifolds, Dehn surgery and the theory of geometric structures of 3-manifolds to study the extent to which nonisotopic knots can be adjacent to each other. A consequence of our main result is that if K is n-adjacent to K' for all n in N, then K and K' are isotopic. This provides a partial verification of the conjecture of V. Vassiliev that finite type knot invariants distinguish all knots. We also show that if no twist about a crossing circle L of a knot K changes the isotopy class of K, then L bounds a disc in the complement of K. This leads to a characterization of nugatory crossings on knots.