Page 1 Next

Displaying 1 – 20 of 69

Showing per page

On a problem in effective knot theory

Stefano Galatolo (1998)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

The following problem is investigated: «Find an elementary function F n : Z Z such that if Γ is a knot diagram with n crossings and the corresponding knot is trivial, then there is a sequence of Reidemeister moves that proves triviality such that at each step we have less than F n crossings». The problem is shown to be equivalent to a problem posed by D. Welsh in [7] and solved by geometrical techniques (normal surfaces).

On constructions of generalized skein modules

Uwe Kaiser (2014)

Banach Center Publications

Józef Przytycki introduced skein modules of 3-manifolds and skein deformation initiating algebraic topology based on knots. We discuss the generalized skein modules of Walker, defined by fields and local relations. Some results by Przytycki are proven in a more general setting of fields defined by decorated cell-complexes in manifolds. A construction of skein theory from embedded TQFT-functors is given, and the corresponding background is developed. The possible coloring of fields by elements of...

On malnormal peripheral subgroups of the fundamental group of a 3 -manifold

Pierre de la Harpe, Claude Weber (2014)

Confluentes Mathematici

Let K be a non-trivial knot in the 3 -sphere, E K its exterior, G K = π 1 ( E K ) its group, and P K = π 1 ( E K ) G K its peripheral subgroup. We show that P K is malnormal in G K , namely that g P K g - 1 P K = { e } for any g G K with g P K , unless K is in one of the following three classes: torus knots, cable knots, and composite knots; these are exactly the classes for which there exist annuli in E K attached to T K which are not boundary parallel (Theorem 1 and Corollary 2). More generally, we characterise malnormal peripheral subgroups in the fundamental group of a...

Currently displaying 1 – 20 of 69

Page 1 Next