
Taking ι→ ∞ and using (11) in mind, we arrive at
lim
ι→∞ DA(αλ(ι), σ) = pb(σ, Fσ).(12)
On the one hand, we assume that αλ=σfor an infi-
nite number of λ∈Nwithout sacrificing generality.
So,
η(stpb(Fαλ,Fσ),DA(αλ, σ)) ≥0.
Thus, as a result of η1, leads us to
ψ(stpb(Fαλ,Fσ)) < ψ(DA(αλ, σ)).
Taking into account the fact that has a non-decreasing
property of ψ,
stpb(Fαλ,Fσ)<DA(αλ, σ).
On the alternative,
pb(σ, Fσ)
≤s(pb(σ, Fαλ) + pb(Fαλ,Fσ)) −pb(Fαλ,Fαλ)
≤spb(σ, Fαλ) + stpb(Fαλ,Fσ)−pb(αλ+1, αλ+1)
< spb(σ, Fαλ) + DA(αλ, σ).
Taking λ→ ∞ in the above inequality and using (11)
and (12), we get
pb(σ, Fσ)≤stlim
λ→∞
pb(Fαλ,Fσ)
<lim
λ→∞
DA(αλ, σ)
=pb(σ, Fσ).
Hence, stlimλ→∞ pb(Fαλ,Fσ) = pb(σ, Fσ).
Therefore, putting ζλ=pb(Fαλ,Fσ)
and ξλ=DA(αλ, σ),using η2it follows
lim supλ→∞ η(stζλ, ξλ)<0,which is a contra-
diction. Then pb(σ, Fσ)=0=pb(σ, σ),that is, σis
a fixed point of F.
Finally, we establish uniqueness of the fixed point.
Indeed, if we can find another point, υ∈ A, υ =σ
such that υ=Fυ,
0 = 1
2smin{pb(υ, Fυ), pb(σ, Fσ)} ≤ pb(υ, σ),
implies
0≤η(stpb(Fυ, Fσ),DA(υ, σ))
< ψ(DA(υ, σ)) −ψ(stpb(Fυ, Fσ))
=ψ(pb(υ, σ)) −ψ(stpb(υ, σ)),
which is a contradiction. Hence, σ=υ.
Corollary 3.3. Let F:A → A be a mapping on
apb-complete partial b-metric space (A, pb, s > 1).
Suppose that ψ∈Υand ϕ: [0,∞)→[0,∞)is a
function such that lim infξ→ξ0ϕ(ξ)>0,for ξ0>0
and ϕ(ξ) = 0 ⇔ξ= 0.If for every ζ, ξ ∈ A
1
2smin {pb(α, Fα), pb(δ, Fδ)} ≤ pb(α, δ)implies
ψ(stpb(Fα, Fδ)) ≤ψ(DA(α, δ)) −ϕ(DA(α, δ)).
Then Fadmits a unique fixed point.
Proof. Taking η(ζ, ξ) = ψ(ξ)−ϕ(ξ)−ψ(ζ)in The-
orem 3.2.
Corollary 3.4. Let F:A → A be a mapping on
apb-complete partial b-metric space (A, pb, s > 1).
Suppose that ψ∈Υand φ: [0,∞)→[0,1) is a
function such that lim supξ→ξ0φ(ξ)<1,for ξ0>0
and φ(ξ) = 0 ⇔ξ= 0.If for every ζ, ξ ∈ A
1
2smin {pb(α, Fα), pb(δ, Fδ)} ≤ pb(α, δ)implies
ψ(stpb(Fα, Fδ)) ≤φ(DA(α, δ))ψ(DA(α, δ)).
Then Fadmits a unique fixed point.
Proof. Taking η(ζ, ξ) = φ(ξ)ψ(ξ)−ψ(ζ)in Theo-
rem 3.2.
Definition 3.5. Let (A, pb, s > 1) be a partial b-
metric space. A mapping F:A → A is called η-
rational contraction of type B, if there exists a func-
tion η∈ Zψsuch that
1
2smin {pb(α, Fα), pb(δ, Fδ)} ≤ pb(α, δ)implies
η(stpb(Fα, Fδ),DB(α, δ)≥0,
(13)
for every α, δ ∈ A,where DBis defined as
DB(α, δ)
=max pb(α, δ), pb(α, Fα), pb(δ, Fδ),
pb(δ, Fδ)pb(α, Fα)
1 + pb(α, δ),pb(δ, Fδ)pb(α, Fα)
1 + pb(Fα, Fδ),
pb(α, Fα) + pb(δ, Fδ)
2s.
(14)
Theorem 3.6. Let (A, pb, s > 1) be a pb-complete
partial b-metric space and F:A → A be a η-
rational contraction of type B. Then Fadmits exactly
one fixed point.
Proof. Let the sequence {αλ}be defined by (3). Be-
cause αλ−1=αλ,for each λ∈N, using logic similar
to that used to prove Theorem 3.2, we have
1
2smin {pb(αλ,Fαλ), pb(αλ+1,Fαλ+1)}
=1
2smin {pb(αλ, αλ+1), pb(αλ+1, αλ+2)}
≤pb(αλ, αλ+1)
WSEAS TRANSACTIONS on MATHEMATICS
DOI: 10.37394/23206.2022.21.54
Sunisa Saiuparad, Kanikar Muangchoo,
Sukjit Tangcharoen, Phannika Mee-On,
Sakulbuth Ekvittayaniphon, Duangkamon Kitkuan