A Seifert algorithm for integral homology spheres
Abstract
From classical knot theory we know that every knot in is the boundary of an oriented, embedded surface. A standard demonstration of this fact achieved by elementary techniques comes from taking a regular projection of any knot and employing Seifert’s constructive algorithm. In this note we give a natural generalization of Seifert’s algorithm to any closed integral homology 3-sphere. The starting point of our algorithm is presenting the handle structure of a Heegaard splitting of a given integral homology sphere as a planar diagram on the boundary of a -ball. (For a well-known example of such a planar presentation, see the Poincaré homology sphere planar presentation in Knots and Links by Rolfsen 3.) An oriented link can then be represented by the regular projection of an oriented -strand tangle. From there we give a natural way to find a “Seifert circle” and associated half-twisted bands.