Dehn Surgery on Arborescent Links

Ying-Qing Wu Abstra t. This paper studies Dehn surgery on a large class of links, called arborescent links. It will be shown that if an arborescent link L is sufficiently complicated, in the sense that it is composed of at least 4 rational tangles T (pi/qi) with all qi > 2, and none of its length 2 tangles are of the form T (1/2q1, 1/2q2), then all complete surgeries on L produce Haken manifolds. The proof needs some result on surgery on knots in tangle spaces. Let T (r/2s, p/2q) = (B, t1 ∪ t2 ∪ K) be a tangle with K a closed circle, and let M = B − IntN(t1 ∪ t2). We will show that if s > 1 and p 6≡ ±1 mod 2q, then ∂M remains incompressible after all nontrivial surgeries on K. Two bridge links are a subclass of arborescent links. For such a link L(p/q), most Dehn surgeries on it are non-Haken. However, it will be shown that all complete surgeries yield manifolds containing essential laminations, unless p/q has a partial fraction decomposition of the form 1/(r − 1/s), in which case it does admit nonlaminar surgeries.