(Λ,sδ)-closure

Definition

• Let (X,τ) be a topological space and A ⊆ X. A point x ∈ X is called (Λ,sδ)-cluster point of A if for every (Λ,sδ)-open set U of X containing x we have A∩U≠∅. The set of all (Λ,sδ)-cluster points is called the (Λ,sδ)-closure of A.

Reference

• Caldas, M.; Ganster, M.; Georgiou, D. N.; Jafari, S.; Moshokoa, S. P., δ-semiopen sets in topology. (English summary), Proceedings of the 19th Summer Conference on Topology and its Applications., Topology Proc. 29 (2005), no. 2, 369–383.