The hexatangle

Abstract

We are interested in knowing what type of manifolds are obtained by doing Dehn surgery on closed pure 3-braids in S 3 . In particular, we want to determine when we get S 3 by surgery on such a link. We consider links which are small closed pure 3-braids; these are the closure of 3-braids of the form ( σ 1 2 e 1 ) ( σ 2 2 f 1 ) ( σ 2 σ 1 σ 2 ) 2 e , where σ 1 , σ 2 are the generators of the 3-braid group and e 1 , f 1 , e are integers. We study Dehn surgeries on these links, and determine exactly which ones admit an integral surgery producing the 3-sphere. This is equivalent to determining the surgeries of some type on a certain six component link L that produce S 3 . The link L is strongly invertible and its exterior double branch covers a certain configuration of arcs and spheres, which we call the hexatangle. Our problem is equivalent to determine which fillings of the spheres by integral tangles produce the trivial knot, which is what we explicitly solve. This hexatangle is a generalization of the pentangle, which is studied in [C.McA. Gordon, J. Luecke, Non-integral toroidal Dehn surgeries, Comm. Anal. Geom. 12 (2004) 417–485].