Notes on the ideal $(a)$

Abstract

For any topologies
$\tau_1 \subseteq \tau_2$, we consider the ideal
of sets $A$ such that for each nonempty
$U \in \tau_2$ there exists $W \in \tau_1$
such that $U \cap W \not= \emptyset$ and
$A \cap U \cap W = \emptyset$.
For $\tau_1$, the standard Euclidean topology,
and for $\tau_2$, the density topology, we obtain the ideal $\aideal$
investigated by Z.Grande and E.Stro\'nska
.