WEAK AND STRONG FORMS OF sT-CONTINUOUS FUNCTIONS

The aim of this paper is to present some properties of sT- continuous functions. Moreover, we obtain a characterization and pre- serving theorems of semi-compact, S-closed and s-closed spaces. The study of semi-open sets and semi-continuity in topological spaces was initiated by Levine (10). In 2009, Noiri et al. (13) defined the notion T-open sets and deduced some results. Quite recently, Al-omari et al. (1) have obtained some properties of T-open sets and characterizations of S-closed spaces. In this paper, we present some properties of sT-continuous functions. Moreover, we obtain characterizations and preserving theorems of semi-compact, S-closed and s-closed spaces. 2. Preliminaries Throughout this paper, (X,) and (Y,) stand for topological spaces on which no separation axiom is assumed unless otherwise stated. For a subset A of X, the closure of A and the interior of A will be denoted by Cl(A) and Int(A), respectively. Let (X,) be a space and S a subset of X. A subset S of X is said to be semi-open (10) if there exists an open set U of X such that U ⊆ S ⊆ Cl(U), or equivalently if S ⊆ Cl(Int(S)). The complement of a semi-open set is said to be semi-closed. The intersection of all semi-closed sets containing S is called the semi-closure of S and is denoted by sCl(S). The semi-interior of S, denoted by sInt(S), is defined by the union of all semi-open sets contained in S. It is verified in (2) that sCl(A) = A ∪ Int(Cl(A)) and sInt(A) = A ∩ Cl(Int(A)) for any subset A ⊆ X. A point x ∈ X is said to be in the -semiclosure of A, denoted by x ∈ -sCl(A), if A ∩ Cl(V ) 6 for each semi-open set V containing x. A subset A ⊆ X is said to be -semiclosed (8) if A = -sCl(A). The complement of a -semiclosed set is called a -semiopen