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Conjugacy for positive permutation braids

Hugh R. Morton, Richard J. Hadji (2005)

Fundamenta Mathematicae

Positive permutation braids on n strings, which are defined to be positive n-braids where each pair of strings crosses at most once, form the elementary but non-trivial building blocks in many studies of conjugacy in the braid groups. We consider conjugacy among these elementary braids which close to knots, and show that those which close to the trivial knot or to the trefoil are all conjugate. All such n-braids with the maximum possible crossing number are also shown to be conjugate. ...

Coverings of S3 branched over iterated torus links.

Carmen Safont (1990)

Revista Matemática de la Universidad Complutense de Madrid

Coverings of S3 branched over iterated torus links appear naturally and very often in Algebraic Geometry. The natural graph-manifold structure of the exterior of an iterated torus link induces a graph-structure in the branched covers. In this paper we give an algorithm to compute valued graphs representing a branched cover given the monodromy representation associated to the covering. The algorithm is completely mechanized in order to be programmed, and can also be used for finding representation...

Crosscaps and knots.

Clark, Bradd Evans (1978)

International Journal of Mathematics and Mathematical Sciences

Cyclic branched coverings and homology 3-spheres with large group actions

Bruno P. Zimmermann (2004)

Fundamenta Mathematicae

We show that, if the covering involution of a 3-manifold M occurring as the 2-fold branched covering of a knot in the 3-sphere is contained in a finite nonabelian simple group G of diffeomorphisms of M, then M is a homology 3-sphere and G isomorphic to the alternating or dodecahedral group 𝔸₅ ≅ PSL(2,5). An example of such a 3-manifold is the spherical Poincaré sphere. We construct hyperbolic analogues of the Poincaré sphere. We also give examples of hyperbolic ℤ₂-homology 3-spheres with PSL(2,q)-actions,...

Cyclic branched coverings of 2-bridge knots.

Alberto Cavicchioli, Beatrice Ruini, Fulvia Spaggiari (1999)

Revista Matemática Complutense

In this paper we study the connections between cyclic presentations of groups and the fundamental group of cyclic branched coverings of 2-bridge knots. Then we show that the topology of these manifolds (and knots) arises, in a natural way, from the algebraic properties of such presentations.

Cyclic branched coverings of knots and homology spheres.

Francisco González-Acuña, Hamish Short (1991)

Revista Matemática de la Universidad Complutense de Madrid

We study cyclic coverings of S3 branched over a knot, and study conditions under which the covering is a homology sphere. We show that the sequence of orders of the first homology groups for a given knot is either periodic of tends to infinity with the order of the covering, a result recently obtained independently by Riley. From our computations it follows that, if surgery on a knot k with less than 10 crossings produces a manifold with cyclic fundamental group, then k is a torus knot.

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