A Sufficient Condition for the Set of Distance Degenerating Handle Additions to be Bounded
摘要
Let V ⋃S W be a Heegaard splitting of M with distance n ≥ 2 and F a boundary component of ∂_V. A simple closed curve J in F is called distance degenerating if the distance of MJ = VJ ⋃S W is less than n, where MJ is obtained by attaching a 2-handle to M along J. In this paper, by considering the distance between J and the image of the essential disks of W under the projection map, we obtain a sufficient condition for the diameter of the set of distance degenerating curves in F to be bounded in C(F). Moreover, for F = ∂M, an upper bound of the diameter of the set of the boundary reducible curves in F is given under some circumstance.