ACTION OF THE CORK TWIST ON FLOER HOMOLOGY
SELMAN AKBULUT, C¸AGRI KARAKURT
Abstract. We utilize the Ozsv´ath-Szab´o contact invariant to detect the action of invo-
lutions on certain homology spheres that are surgeries on symmetric links, generalizing a
previous result of Akbulut and Durusoy. Potentially this may be useful to detect different
smooth structures on 4-manifolds by cork twisting operation.
Any two different smooth structures of a closed simply connected 4-manifold are related
to each other by a cork twisting operation , and the cork can be assumed to be a Stein
manifold  (see  and  for applications). A quick way to generate corks, which was
used in , is from symmetric links as follows: Let L be a link in S3
with two components
K1 K2. Suppose that L satisfies the following:
(1) Both components K1 and K2 are unknotted.
(2) There is an involution of S3
exchanging K1 and K2.
(3) The linking number of K1 and K2 is ±1 (for some choice of orientations).
From this we can construct a 4manifold W(L) by carving out a disk bounded by K1 from
4ball, and attaching a 2handle along K2 with framing 0. Therefore a handlebody diagram