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Wirtinger presentations for higher dimensional manifold knots obtained from diagrams

Seiichi Kamada (2001)

Fundamenta Mathematicae

A Wirtinger presentation of a knot group is obtained from a diagram of the knot. T. Yajima showed that for a 2-knot or a closed oriented surface embedded in the Euclidean 4-space, a Wirtinger presentation of the knot group is obtained from a diagram in an analogous way. J. S. Carter and M. Saito generalized the method to non-orientable surfaces in 4-space by cutting non-orientable sheets of their diagrams by some arcs. We give a modification to their method so that one does not need to find and...

Yamada polynomial and crossing number of spatial graphs.

Tomoe Motohashi, Yoshiyuki Ohyama, Kouki Taniyama (1994)

Revista Matemática de la Universidad Complutense de Madrid

In this paper we estimate the crossing number of a flat vertex graph in 3-space in terms of the reduced degree of its Yamada polynomial.

θ -curves inducing two different knots with the same 2 -fold branched covering spaces

Soo Hwan Kim, Yangkok Kim (2003)

Bollettino dell'Unione Matematica Italiana

For a knot K with a strong inversion i induced by an unknotting tunnel, we have a double covering projection Π : S 3 S 3 / i branched over a trivial knot Π fix i , where fix i is the axis of i . Then a set Π fix i K is called a θ -curve. We construct θ -curves and the Z 2 Z 2 cyclic branched coverings over θ -curves, having two non-isotopic Heegaard decompositions which are one stable equivalent.

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