Abstract

An ideal on a set X is a nonempty collection of subsets of X closed under the operations of subset (heredity) and finite unions (additivity). Given a topological space (X,τ) an ideal on X and AX, ψ(A) is defined as {Uτ:UA}. A topology, denoted τ*, finer than τ is generated by the basis {UI:Uτ,I}, and a topology, denoted ψ(τ), coarser than τ is generated by the basis ψ(τ)={ψ(U):Uτ}. The notation (X,τ,ϑ) denotes a topological space (X,τ) with an ideal on X. A bijection f:(X,τ,)(Y,σ,J) is called a *-homeomorphism if f:(X,τ*)(Y,σ*) is a homeomorphism, and is called a ψ-homeomorphism if f:(X,ψ(τ))(Y,ψ(σ)) is a homeomorphism. Properties preserved by *-homeomorphisms are studied as well as necessary and sufficient conditions for a ψ -homeomorphism to be a *-homeomorphism. The semi-homeomorphisms and semi-topological properties of Crossley and Hildebrand [Fund. Math., LXXIV (1972), 233-254] are shown to be special case.