English

Ideal-Aura Topological Spaces, New Local Functions, and Generalized Open Sets

General Topology 2026-02-18 v2

Abstract

We combine an ideal topological space (X,τ,I)(X, \tau, \mathcal{I}) with a scope function a:Xτ\mathfrak{a}: X \to \tau, xa(x)x \in \mathfrak{a}(x), to form what we call an ideal-aura topological space (X,τ,I,a)(X, \tau, \mathcal{I}, \mathfrak{a}). The central new object is the aura-local function Aa(I)={xX:a(x)AI}A^{\mathfrak{a}}(\mathcal{I}) = \{x \in X : \mathfrak{a}(x) \cap A \notin \mathcal{I}\}, which extends the Jankovic-Hamlett local function: we always have A(I,τ)Aa(I)A^{*}(\mathcal{I}, \tau) \subseteq A^{\mathfrak{a}}(\mathcal{I}). The closure cla(A)=AAa(I)\operatorname{cl}^{*}_{\mathfrak{a}}(A) = A \cup A^{\mathfrak{a}}(\mathcal{I}) is an additive Cech closure operator that, in general, fails to be idempotent; we prove that idempotency is equivalent to transitivity of a\mathfrak{a}. The resulting Cech topology τa\tau^{*}_{\mathfrak{a}} sits in the chain τaτaτ\tau_{\mathfrak{a}} \subseteq \tau^{*}_{\mathfrak{a}} \subseteq \tau^{*}, interpolating between the pure aura topology and the classical ideal topology. We introduce a ψa\psi_{\mathfrak{a}}-operator and use it to give an alternative description of τa\tau^{*}_{\mathfrak{a}}. Five classes of Ia\mathcal{I}\mathfrak{a}-generalized open sets are defined and arranged in a hierarchy, with strict inclusions separated by counterexamples. Decomposition theorems for Ia\mathcal{I}\mathfrak{a}-continuity are proved. Three special cases are examined: the trivial ideal recovers the pure aura topology, the improper ideal gives the discrete topology, and the ideal of finite sets exhibits a localization phenomenon.

Cite

@article{arxiv.2602.07692,
  title  = {Ideal-Aura Topological Spaces, New Local Functions, and Generalized Open Sets},
  author = {Ahu Acikgoz and Murad Ozkoc},
  journal= {arXiv preprint arXiv:2602.07692},
  year   = {2026}
}

Comments

19 pages. Third paper in the Aura Topological Spaces series

R2 v1 2026-07-01T10:26:15.958Z