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Outermost forks and a theorem of Jaco. (English) Zbl 0589.57011
Combinatorial methods in topology and algebraic geometry, Proc. Conf. Hon. A. M. Stone, Rochester/N. Y. 1982, Contemp. Math. 44, 189-193 (1985).
[For the entire collection see Zbl 0564.00013.]
The author gives another proof of a theorem due to Jaco: Let M be a compact orientable 3-manifold. If the boundary of M is compressible, but contains a simple closed curve J whose complement is incompressible, then adding a 2-handle along J produces a 3-manifold with incompressible boundary. The proof adds nothing really new, but does provide a clear exposition of the use of the technique of ”outermost forks” for analyzing intersections of disks and surfaces.
Reviewer: N.Smythe

##### MSC:
 57N10 Topology of general $$3$$-manifolds (MSC2010) 57R65 Surgery and handlebodies