2. Preliminaries
We recall the following definitions:
Definition 2.1. A subset A of a topological space (X, τ) is called
(i) Generalized closed (briefly g-closed)[6] if cl(A) ⊆ G whenever A ⊆ G and G is open in X.
(ii) Semi-generalized closed (briefly sg-closed)[3] if scl(A) ⊆ G whenever A ⊆ G and G is semiopen in X.
(iii) Generalized semiclosed (briefly gs-closed)[2] if scl(A) ⊆ G whenever A ⊆ G and G is open in X.
(iv) α-closed[8] if cl(int(cl(A))) ⊆ A .
(v) α-generalized closed (briefly αg-closed)[9] if clα(A)⊆ G whenever A ⊆ G and G is open in X.
(vi) Generalized α-closed (briefly gα-closed)[10] if spcl (A) ⊆ G whenever A ⊆ G and G is open in X.
(vii) Generalized semi-preclosed (briefly gsp-closed)[2] if scl(A) ⊆ G whenever A ⊆ G and G is open in X.
(viii) Strongly generalized closed (briefly strongly g-closed ) [12] if cl(A) ⊆ G whenever A ⊆ G and G is g-open in X.
(ix) Preclosed[11] if cl(int(A)) ⊆ A.
(x) Semi-closed[7] if int(cl(A)) ⊆ A.
(xi) Semi-preclosed (briefly sp-closed)[1] if int(cl(int(A))) ⊆ A.
The complements of the above mentioned sets are called
their respective open sets.
Definition 2.2. For the subset A of a topological X, the generalized closure operator cl*[5] is defined by the
intersection of all g-closed sets containing A.
Definition 2.3. For the subset A of a topological X, the
topology τ* is defined by τ* = {G : cl*(GC) = GC }
Definition 2.4. For the subset A of a topological X,
(i) the semi-closure of A (briefly scl(A))[7] is defined as the intersection of all semi-closed sets containing A.
(ii) the semi-preclosure of A (briefly spcl(A))[1] is defined as the intersection of all semi-preclosed sets containing A.
(iii) the α-closure of A (briefly clα(A))[8] is defined as the intersection of all α-closed sets containing A.