ical space with an ideal Ion U, the set operator
nCl∗is called anano ∗-closure and is defined as :
nCl∗(A) = A∪A∗
n, for A⊆X.
Theorem 3.7. [11] The set operator nCl∗meets the
requirement listed below:
(i) A⊆nCl∗(A),
(ii) nCl∗(ϕ) = ϕand nCl∗(U) = U,
(iii) If A⊆B, then nCl∗(A)⊆nCl∗(B),
(iv) nCl∗(A)∪nCl∗(B) = nCl∗(A∪B),
(v) nCl∗(nCl∗(A)) = nCl∗(A).
Definition 3.8. ([5], [7]) Let (U, τR(X), I)be anano
ideal topological space, then A⊆Uis said to be :
(i) Nano regular I-open (nano RI-open ) if A=
nInt(nCl∗(A)),
(ii) Nano regular I-closed(nano RI-closed) if its com-
plement is nano RI-open
(iii) Nano semi I-open if A=nCl(nInt∗(A)),
(iv) Nano semi I-closed if its complement is nano
semi I-open ,
(v) Nano αI-open if A⊆nInt(nCl∗(nInt(A))),
(vi) Nano αI-closed if its complement is nano αI-
open ,
(vii) Nano pre-I-open if A⊆nInt(nCl∗(A)),
(viii) Nano pre-I-closed if its complement is nano
pre-I-open ,
(ix) Nano βI-open if A⊆nCl(nInt(nCl∗(A))),
(x) Nano βI-closed if its complement is nano βI-open
.
Definition 3.9. [6] An ideal Iin anano ideal topo-
logical space (U, τR(X), I)is called τR(X)- codense
ideal if τR(X)∩I={ϕ}.
Definition 3.10. [6] Asubset Ain anano ideal topo-
logical space (U, τR(x), I)is said to be :
(i) Nano ⋆-dense-in-itself if A⊆A∗
n,
(ii) Nano ⋆-closed if A∗
n⊆A,
(iii) Nano ⋆-perfect if A=A∗
n,
(iv) Nano I-dense if A∗
n=U.
The connections between the aforementioned nano
sets are depicted in the diagram below.
Nano ⋆-dense-in-itself ⇐Nano ⋆-perfect ⇒
Nano ⋆-closed
The examples that follow demonstrate that the dia-
gram’s converse implications cannot be satisfied.
Example 3.11. Let U={a, b, c, d}be the uni-
verse, U/R={{a},{c},{b, d}} be the family of
equivalence classes of Uby the equivalence rela-
tion Rand X={a, b}. Then one can deduce that
LR(X) = {a}, HR(X) = {a, b, d},then the nano
topology τR(X) = {U, ϕ, {a},{b, d},{a, b, d}}. For
I ={ϕ, {a}}, we have :
(i) If A={a, c}, then parimala et al. [6] observed
that A∗
n={c}. Here Ais anano ⋆closed, but not
nano ⋆-perfect .
(ii) If B={c, d}, then we have B∗
n={b, c, d}. So
Bis anano ⋆-dense-in-itself but not nano ⋆-perfect.
4 More on nano I-open sets
Definition 4.1. [11] Asubset Ain anano ideal topo-
logical space (U, τR(x), I)is said to be nano I-open
if A⊆nINT (A∗
n).Asubset F⊆(U, τR(X), I)is
said to nano I-closed if its complement U\Fis nano
I-open .
We connote by NIO(U, τR(X), I) = {A⊆U:
A⊆nInt(A∗
n)}or simply write NIO(U, τR(X))
or NIO(U)for N IO(U, τR(X), I)when there is no
possibility of mistake with the ideal.
The largest nano I-open set contained in Ais
known as the nano I-interior of A, denoted by nI-
Int(A).
Remark 4.2. The following example demonstrates
how nano I-openness and nano openness are concep-
tually distinct.
Example 4.3. Let U={a, b, c, d}be the
universe, X={a, b} ⊂ Uand U/R=
{{a},{c},{b, d}}. This can be extrapolated as:
LR(X) = {a},HR(X) = {a, b, d}. Then τR(X) =
{U, ϕ, {a},{b, d},{a, b, d}}. For I={ϕ, {a}}.
(i) Set A={a, b, d}, we have A∗
n={b, c, d}and
nInt(A∗
n) = {b, d}, that is A⊈nInt(A∗
n). As can
be seen, Ais nano open but nano I-open.
(ii) Set B={d}, we have B∗
n={b, c, d}and
nInt(B∗
n) = {b, c, d}, that is B⊆nInt(B∗
n).Ais
nano I-open but not nano open, as evidenced by this.
Remark 4.4. The following example demonstrates
that every nano I-open set is anano preopen set and
that, generally speaking, the opposite is not true.
Example 4.5. Let U={a, b, c, d}be the uni-
verse, and let X={a, b} ⊂ Uand U/R=
{{a},{c},{b, d}}. This can be presumed as:
LR(X) = {a}, HR(X) = {a, b, d}. Then τR(X) =
{U, ϕ, {a},{b, d},{a, b, d}}. For I={ϕ, {a}}
and A={a, b, c}, we have A∗
n={b, c, d}and
nInt(A∗
n) = {b, d}, that is A⊈nInt(A∗
n), but
nCl(A) = Uand nInt(nCl(A)) = U.Ais anano
preopen, but not nano I-open, as demonstratedby this.
Proposition 4.6. Nano I-open also refers to the arbi-
trary union of nano I-open sets.
Proof. Let (U, τR(X), I)be a nano ideal topologi-
cal space and Wi∈NIO(U, τR(X), I)for i∈ ▽;
this implies that for every i∈ ▽, W, ∈nInt((Wi)∗
n)
and so ∪i{Wi:i∈ ▽} ⊆ ∪i(nInt((Wi)∗
n)⊆
nIn(∪i((Wi)∗
n)⊆nIn(∪i((Wi))∗
nfor every i∈ ▽.
Hence ∪i{Wi:i∈ ▽} ∈ NIO(U, τR(X), I)
Theorem 4.7. [11] Let (U, τR(X), I)be anano ideal
topological space and A, B ⊆U.Then:
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2024.23.31
Arafa A. Nasef, Radwan Abu-Gdairi