
that u1, u2∈U1since u1is in each γnbd of u2,
i. e., u1∈Mwhen u2∈γInt(M). Therefore
u2∈γCl(K1)when u1∈K1, and especially since
u1∈ {u1},u2∈γCl({u1}).As a consequence,
u1∈γCl({u2}). Hence if u2∈K2, therefore
u1∈γCl({u2})⊆γCl(K2), as γCl is γIso. Then,
if u1∈γCl(K3), then u2∈K3, that is, u2is in each
γnbdofu1. Then, (2) implies (3).
Now, assume that (U1, γCl)is R0γand u1∈
γCl({u2})such that γCl is γIso,u1∈γCl(K2)
whenever u2∈K2or, u2is in each γnbd of u1
where (U1, γCl)is R0γ,u1∈γInt(M). Then,
u2∈γCl(K1)whenever u1∈K1, and especially
since u1∈ {u1},u2∈γCl({u1}). Hence, (3) =⇒
(2).
Theorem 3.5. Let Wbe a set of unordered pairs of
subsets of a set of U1. Then:
(1) If K1⊆K2and (K2, K3)∈W, then
(K1, K3)∈W,∀K1, K2, K3⊆U1;
(2) If ({u1}, K2)∈W,∀u1∈K1and
({u2}, K1)∈W, ∀u2∈K2, then (K1, K2)∈
W,∀K1, K2, K3⊆U1. Then there is a unique
pointwise γsym,γIso and γCl mappings γCl
on U1which γCl-sep the elements of W.
Proof. . Define γCl by γCl(K1) = {u1∈U1:
({u2}, K1) /∈W}for each K1⊆U1. If K1⊆
K2⊆U1and u1∈γCl(K1), then ({u2}, K1) /∈
W, thus ({u1}, K2) /∈W, meaning that, u1∈
γCl(K2). Then, γCl({u1})is γIso, Moreover,
u1∈γCl({u2})iff ({u1},{u2}) /∈Wiff u2∈
γCl({u1}). Hence γCl is pointwise γsym. Let
(K1, K2)∈W. Therefore K1∩{γCl(K2)}=
K1∩{u1∈U1: ({u1}, K2) /∈W}={u1∈K1:
({u1}, K1) /∈W}=ϕ. Similarly, γCl(K1)∩K2=
ϕ. Then, if (K1, K2)∈W, then K1, and K2are
γCl-sep.
Now, Let K1and K2be γCl-sep. Then {u1∈K1:
({u1}, K2) /∈W}=K1∩γCl(K2) = ϕand {u1∈
K2: ({u2}, K1) /∈W}=γCl{K1∩K2=ϕ.
Thus, ({u1}, K2)∈W, ∀u1∈K1and ({u2}, K1)∈
W, ∀u2∈K2. Then, (K1, K2)∈W.
Many features of γCl mappings can be stated wise
the sets they separate, as shown below:
Theorem 3.6. If Wis the pairs of γCl-sep sets of a
generalized γCl structure (U1, γCl)in which γExt
points are γCl-sep, then γCl is
(1) γ-grounded iff ∀u1∈U1,({u1}, ϕ)∈W.
(2) γ-enlarging iff ∀(K1, K2)∈W,K1∩K2=ϕ.
(3) γ-sub linear iff (K1, K2∪K3)∈Wwhenever
(K1, K2)∈Wand (K1, K3)∈W.
In addition, if γCl is γ-enlarging and for
K1, K2⊆U1.({u1}, K1) /∈Wwhenever
({u1}, K2) /∈W}and ({u2}, K1) /∈W, ∀u2∈
K2, then γCl is γ-idempotent. Also,if γCl-Iso
and γ-idepotent, then ({u1}, K1) /∈W
whenever ({u1}, K1) /∈Wand ({u2}, K1) /∈
W, ∀u2∈K2.
Proof. . By Theorem 3.1, γCl(K1) = {u1∈
U1: ({u1}, K1) /∈W}for each K1⊆U1.
Let ∀u1∈U1,({u1}, ϕ)∈W. Therefore
γCl(ϕ) = {u1∈U1,({u1}, ϕ) /∈W}=ϕ.
Then γCl is γ-grounded. Conversely, if ϕ=
γCl(ϕ) = {u1∈U1,({u1}, ϕ) /∈W}, and hence
({u1}, ϕ)∈W, for every u1∈U1. Let for each
(K1, K2)∈W,K1∩K2=ϕ. Since ({a}, K1) /∈W
if a∈K1,K1⊆γCl(K1),∀K1⊆U1. Then
γCl is γ-enlarging. Conversely, suppose that γCl
is γ-enlarging and (K1, K2)∈W. Therefore
K1∩K2⊆γCl(K1)∩K2=ϕ.
Let (K1, K2∪K3)∈Wwhenever (K1, K2)∈W
and (K1, K3)∈W, and Let u1∈U1and
K2, K3⊆U1where ({u1}, K2∪K3) /∈W.
Therefore ({u1}, K2) /∈Wor ({u1}, K3) /∈W.
Thus γCl(K2∪K3)⊆γCl(K2)∪γCl(K3).
Hence, γCl is γ-sublinear.
Conversely, let γCl be γ-sublinear,
and (K1, K2),(K1, K3)∈W.
Therefore γCl(K2∪K3)∩K1⊆
(γCl(K2)∪{γCl(K3)) ∩K1=
(γCl(K2)∩K1)∪(γCl(K3)∩K1) =
ϕand (K2∪K3)∩γCl(K1) =
(K2∩γCl(K1)) ∪(K3∩γCl(K1)) = ϕ. Assume
that γCl is γ-enlarging and let ({u1}, K1) /∈W
whenever ({u2}, K2) /∈Wand ({u2}, K1) /∈
W, ∀u2∈K2, then γCl(γCl(K1)) ⊆γCl(K1). If
u1∈ {γCl{γCl(K1)}}, hence ({u1}, γCl(K1)) /∈
W,({u2}, K1) /∈W, ∀u2∈γCl(K1), and hence
({u1}, K1) /∈W. Where γCl is γ-enlarging,
therefore γCl(K1)⊆γCl(γCl(K1)). Then,
γCl(γCl(K1)) = γCl(K1),∀K1⊆U1. Lastly,
let’s say that γCl be γIso and γ-idempotent.
Suppose that u1∈U1and K1, K2⊆U1
since ({u1}, K2) /∈Wand ∀u2∈K2,
({u2}, K1) /∈W, then u1∈γCl(K2)and ∀u2∈K2,
u2∈γCl(K1), (i. e., K2⊆γCl(K1). Then,
u1∈γCl(K2)⊆γCl(γCl(K1)) = γCl(K1).
Definition 3.7. If (U1,(γCl)U1)and (U2,(γCl)U2)
are generalized γCl structures, then a mapping T:
U1→U2is called:
(1) γCl preserving if T((γCl)U1(K1)) ⊆
(γCl)U2(T(K1)),∀K1⊆U1.
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2024.23.70
M. Badr, Radwan Abu-Gdairi