 
Summary: Journal of GĻokova Geometry Topology
Volume 2 (2008) 4082
Corks, Plugs and exotic structures
Selman Akbulut and Kouichi Yasui
Abstract. We discuss corks, and introduce new objects which we call plugs. Though
plugs are fundamentally different objects, they also detect exotic smooth structures
in 4manifolds like corks. We discuss relation between corks, plugs and rational blow
downs. We show how to detect corks and plugs inside of some exotic manifolds.
Furthermore, we construct knotted corks and plugs.
1. Introduction
Let Wn, Wn and Wm,n be the smooth 4manifolds given by Figure 1. Notice that W1
is a version of the manifold defined in [22] by Mazur, and Wn is the "positron" intro
duced by the first author and Matveyev [8]. The first author [1] proved that E(2)#CP
2
changes its diffeomorphism type by regluing an imbedded copy of W1 inside via a natu
ral involution on the boundary W1. This was later generalized to E(n)#CP
2
(n 2)
by BizacaGompf [11]. The following general theorem was first proved independently by
Matveyev [21], CurtisFreedmanHsiangStong [13], and later on strengthened by the first
