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Article

Solving Some Integral and Fractional Differential Equations via Neutrosophic Pentagonal Metric Space

1
Department of Mathematics, Saveetha School of Engineering, Saveetha Institute of Medical and Technical Sciences, Chennai 602105, Tamil Nadu, India
2
Faculty of Electrical Engineering, University of Banja Luka, Patre 5, 78000 Banja Luka, Bosnia and Herzegovina
3
Department of Mathematics and Sciences, Prince Sultan University, Riyadh 11586, Saudi Arabia
4
School of Computer, Data and Mathematical Sciences, Western Sydney University, Sydney 2150, Australia
*
Author to whom correspondence should be addressed.
Axioms 2023, 12(8), 758; https://doi.org/10.3390/axioms12080758
Submission received: 17 May 2023 / Revised: 13 July 2023 / Accepted: 27 July 2023 / Published: 1 August 2023
(This article belongs to the Special Issue Fixed Point Theory and Its Related Topics IV)

Abstract

:
In this paper, we first introduce the notion of neutrosophic pentagonal metric space. We prove several interesting results for some classes contraction mappings and prove some fixed point theorems in neutrosophic pentagonal metric space. Finally, we prove the uniqueness and existence of the integral equation and fractional differential equation to support our main result.

1. Introduction

A fuzzy set is a category of items with a continuum of membership levels between zero and one. The concept of a fuzzy set was first introduced by Zadeh [1], who also provided a useful starting point for the development of a conceptual framework that, while similar to the framework used for sets in many ways, is more general and may have a wider range of applications, particularly in the fields of pattern classification and information processing. The study of statistical metric spaces and an examination of the continuous characteristics of the distance function were both continued by Schweizer and Sklar in [2]. Fuzzy metric spaces (shortly, Fuzzy MS) were proposed by Kramosil and Michálek in [3], who also expanded on the notion of convergence that is typically used to determine whether a generalization is appropriate. On fuzzy double-controlled MSs, Azmi [4] developed the novel idea of  ( α Π ) -fuzzy contractive mappings and illustrated various fixed-point results. In the framework of extended fuzzy b-MSs, various generalized fixed point findings of Banach and Ćirić type are established by Rome et al. [5]. A Hausdorff fuzzy b-MS is described by Batul et al. [6]. A few fixed point results for multivalued mappings in G-complete fuzzy b-MSs that satisfy an appropriate contractiveness criterion are established using the novel idea. Numerous fixed point theorems in fuzzy b-MSs make up Rakić et al. [7]. They provided a necessary condition for a sequence to be Cauchy in the fuzzy b-MS, which was a significant result. By using a control function  α ( x , y )  of the right-hand side of the b-triangle inequality, Mlaiki [8] created a new extension of b-MSs known as controlled metric type spaces. Controlled fuzzy MS is a brand-new development of Sezen’s [9] work on fuzzy metrics. Additionally, they demonstrated a new fixed point theorem and a Banach-type fixed point theorem for some fulfilling self-mappings. see [10,11,12,13,14,15,16]. Grabiec [17] extended two fixed point theorems of Banach and Edelstein to contractive mappings of complete and compact fuzzy MSs, respectively. In order to established some fixed point theorems, Rehman et al. [18] defined  α -admissible and  α - Π -fuzzy cone contraction in fuzzy cone MS. Finally, he used theoretical results to show that a nonlinear integral equation has a solution.
Park [19] created an intuitionistic fuzzy MS delta membership and nonmembership functions. The concept of an intuitionistic fuzzy b-MS was first proposed by Konwar [20], who also demonstrated a number of fixed point theorems. Neutosophic MSs, which are initialized to handle membership, nonmembership, and naturalness, were introduced by Kirişci and Simsek in their [21] paper. Simsek and Kirişci [22] demonstrated various fixed point results in the context of neutrosophic MSs. Fixed point findings in neutrosophic MSs were demonstrated by Sowndrarajan et al. [23]. Itoh [24] showed a usage for random differential equations in Banach spaces.
In this article, we introduce the neutrosophic pentagonal MS (also known as NPMS) and demonstrate a few fixed point conclusions. The following are the primary goals of this work:
  • To introduce the notion of neutrosophic pentagonal MS;
  • To prove several fixed-point theorems for contraction mappings;
  • Show the existence of a unique solution of an integral equation;
  • Show the existence of a unique solution of a fractional differential equation.

2. Preliminaries

Here, we’ll go over some fundamental terms that will be useful for the key results.
Definition 1
([19]). Let  : [ 0 , 1 ] 2 [ 0 , 1 ]  be a binary operation is said to be a continuous triangle norm if:
(1) 
ω ^ h ˘ = h ˘ ω ^ , ω ^ , h ˘ [ 0 , 1 ] ;
(2) 
is continuous;
(3) 
ω ^ 1 = ω ^ , ω ^ [ 0 , 1 ] ;
(4) 
( ω ^ h ˘ ) μ ˜ = ω ^ ( h ˘ μ ˜ ) , ∀  ω ^ , h ˘ , μ ˜ [ 0 , 1 ] ;
(5) 
If  ω ^ μ ˜  and  h ˘ ς , ∀   ω ^ , h ˘ , μ ˜ , ς [ 0 , 1 ] , then  ω ^ h ˘ μ ˜ ς .
Definition 2
([19]). Let  : [ 0 , 1 ] 2 [ 0 , 1 ]  be a binary operation is said to be a continuous triangle co-norm if:
(1) 
ω ^ h ˘ = h ˘ ω ^ , ∀  ω ^ , h ˘ [ 0 , 1 ] ;
(2) 
• is continuous;
(3) 
ω ^ 0 = 0 , ∀  ω ^ [ 0 , 1 ] ;
(4) 
( ω ^ h ˘ ) μ ˜ = ω ^ ( h ˘ μ ˜ ) , ∀  ω ^ , h ˘ , μ ˜ [ 0 , 1 ] ;
(5) 
If  ω ^ μ ˜  and   μ ˜ ς with  ω ^ , h ˘ , μ ˜ , ς [ 0 , 1 ] , then  ω ^ h ˘ μ ˜ ς .
Definition 3
([24]). Let  χ , F : K × K [ 1 , + )  be given two non-comparable functions, if  : K × K [ 0 , + )  satisfies axioms:
(a) 
( U , W ) = 0  iff  U = W ;
(b) 
( U , W ) = ( W , U ) ;
(c) 
( U , W ) χ ( U , £ ) ( U , £ ) + F ( £ , W ) ( £ , W ) ;
 ∀  U , W , £ K , then,  ( K , )  is known to be a double controlled MS (shortly, DCMS).
Definition 4
([25]). Let  K  and  χ , F : K × K [ 1 , + )  be known non-comparable functions. Andis a continuous t-norm also Λ be a fuzzy set on  K × K × ( 0 , + )  is said to be fuzzy double controlled metric on  K , ∀   U , W , £ K  if:
(i)   
Λ ( U , W , 0 ) = 0 ;
(ii)  
Λ ( U , W , Γ ) = 1 Γ > 0 , ⇔ U = W ;
(iii) 
Λ ( U , W , Γ ) = Λ ( W , U , Γ ) ;
(iv)  
Λ ( U , £ , Γ + Γ ) Λ U , W , Γ χ ( U , W ) Λ W , £ , Γ F ( W , £ ) ;
(v)   
Λ ( U , W , · ) : ( 0 , + ) [ 0 , 1 ]  is continuous on left.
Then,  ( K , Λ , N , )  is known to be a fuzzy DCMS.
Definition 5
([20]). Let  K . Let ★, • are the continuous t-norm, continuous t-co-norm respectively,  1  and  Λ , N  be fuzzy sets on  K × K × ( 0 , + ) . If  ( K , Λ , N , , )  fullfils all  U , W K  and  g ˇ , Γ > 0 :
(I)     
Λ ( U , W , Γ ) + Π ( U , W , Γ ) 1 ;
(II)    
0 < Λ ( U , W , Γ ) ;
(III)   
Λ ( U , W , Γ ) = 1 U = W ;
(IV)    
Λ ( U , W , Γ ) = Λ ( W , U , Γ ) ;
(V)     
Λ ( U , £ , ( Γ + g ˇ ) ) Λ ( U , W , Γ ) Λ ( W , £ , g ˇ ) ;
(VI)    
Λ ( U , W , · )  is a non-decreasing function of  R +  and  lim Γ + Λ ( U , W , Γ ) = 1 ;
(VII)   
0 < Π ( U , W , Γ ) ;
(VIII)  
Π ( U , W , Γ ) = 0 U = W ;
(IX)    
Π ( U , W , Γ ) = Π ( W , U , Γ ) ;
(X)     
Π ( U , £ , ( Γ + g ˇ ) ) Π ( U , W , Γ ) Π ( W , £ , g ˇ ) ;
(XI)    
Π ( U , W , · )  is a non-increasing function of  R +  and  lim Γ + Π ( U , W , Γ ) = 0 ,
Then,  ( K , Λ , Π , , )  is an intuitionistic fuzzy ♭-MS.
Definition 6
([21]). Let  K , ★, • are the continuous t-norm, continuous t-co-norm respectively, and  Λ , Π , S  are neutrosophic sets (shortly, N-sets) on  K × K × ( 0 , + )  is known to be a neutrosophic metric on  K , if for all  U , W , £ K , the following axioms are fulfilled:
(1)   
Λ ( U , W , Γ ) + Π ( U , W , Γ ) + S ( U , W , Γ ) 3 ;
(2)   
0 < Λ ( U , W , Γ ) ;
(3)   
Λ ( U , W , Γ ) = 1 Γ > 0 , ⇔ U = W ;
(4)   
Λ ( U , W , Γ ) = Λ ( W , U , Γ ) ;
(5)   
Λ ( U , £ , Γ + g ˇ ) Λ ( U , W , Γ ) Λ ( W , £ , g ˇ ) ;
(6)   
Λ ( U , W , · ) : ( 0 , + ) [ 0 , 1 ]  is continuous and  lim Γ + Λ ( U , W , Γ ) = 1 ;
(7)   
1 < Π ( U , W , Γ ) ;
(8)   
Π ( U , W , Γ ) = 0 Γ > 0 , ⇔ U = W ;
(9)   
Π ( U , W , Γ ) = Π ( W , U , Γ ) ;
(10) 
Π ( U , £ , Γ + g ˇ ) Π ( U , W , Γ ) Π ( W , £ , g ˇ ) ;
(11) 
Π ( U , W , · ) : ( 0 , + ) [ 0 , 1 ]  is continuous and  lim Γ + Π ( U , W , Γ ) = 0 ;
(12) 
1 < S ( U , W , Γ ) ;
(13) 
S ( U , W , Γ ) = 0 Γ > 0 , ⇔ U = W ;
(14) 
S ( U , W , Γ ) = S ( W , U , Γ ) ;
(15) 
S ( U , £ , Γ + g ˇ ) S ( U , W , Γ ) S ( W , £ , g ˇ ) ;
(16) 
S ( U , W , · ) : ( 0 , + ) [ 0 , 1 ]  is continuous and  lim Γ + S ( U , W , Γ ) = 0 ;
(17) 
If  Γ 0 , then  Λ ( U , W , Γ ) = 0 , Π ( U , W , Γ ) = 0 ;
Then,  ( K , Λ , Π , S , , )  is known to be a neutrosophic MS.
In this article, we define NPMS and demonstrate fixed point theorems.

3. Main Results

This section presents NPMS and illustrates some fixed-point theorems.
Definition 7.
Let  K  and function  χ : K × K [ 1 , + )  be non-comparable, ★, • are the continuous t-norm, continuous t-co-norm respectively, and  Λ , Π , M  be N-sets on  K × K × ( 0 , + )  is known to be a neutrosophic pentagonal metric on  K , if for any  U , £ K  and all distinct  x ˇ , W , £ K , the following axioms are fulfilled:
(i)    
Λ ( U , W , Γ ) + Π ( U , W , Γ ) + M ( U , W , Γ ) 3 ;
(ii)    
0 < Λ ( U , W , Γ ) ;
(iii)   
Λ ( U , W , Γ ) = 1 Γ > 0 , ⇔ U = W ;
(iv)    
Λ ( U , W , Γ ) = Λ ( W , U , Γ ) ;
(v)     
Λ ( U , £ , Γ + g ˇ + k ˇ + e ˇ ) Λ U , W , Γ Λ W , x ˇ , g ˇ Λ x ˇ , y ˇ , k ˇ Λ y ˇ , £ , e ˇ ;
(vi)    
Λ ( U , W , · ) : ( 0 , + ) [ 0 , 1 ]  is continuous and  lim Γ + Λ ( U , W , Γ ) = 1 ;
(vii)   
1 < Π ( U , W , Γ ) ;
(viii) 
Π ( U , W , Γ ) = 0 Γ > 0 , ⇔ U = W ;
(ix)    
Π ( U , W , Γ ) = Π ( W , U , Γ ) ;
(x)     
Π ( U , £ , Γ + g ˇ + k ˇ + e ˇ ) Π U , W , Γ Π W , x ˇ , g ˇ Π x ˇ , y ˇ , k ˇ Π y ˇ , £ , e ˇ ;
(xi)    
Π ( U , W , · ) : ( 0 , + ) [ 0 , 1 ]  is continuous and  lim Γ + Π ( U , W , Γ ) = 0 ;
(xii)   
1 < M ( U , W , Γ ) ;
(xiii)  
M ( U , W , Γ ) = 0 Γ > 0 , ⇔ U = W ;
(xiv)   
M ( U , W , Γ ) = M ( W , U , Γ ) ;
(xv)    
M ( U , £ , Γ + g ˇ + k ˇ + e ˇ ) M U , W , Γ M W , x ˇ , g ˇ M x ˇ , y ˇ , k ˇ M y ˇ , £ , e ˇ ;
(xvi)   
M ( U , W , · ) : ( 0 , + ) [ 0 , 1 ]  is continuous and  lim Γ + M ( U , W , Γ ) = 0 ;
(xvii)  
If  Γ 0 , then  Λ ( U , W , Γ ) = 0 , Π ( U , W , Γ ) = 1  and  S ( U , W , Γ ) = 1 .
Then,  ( K , Λ , Π , M , , )  is said to be a NPMS.
Example 1.
Let  K = { 1 , 2 , 3 , 4 } . Define  Λ , Π , M : K × K × ( 0 , + ) [ 0 , 1 ]  as
Λ ( U , W , Γ ) = 1 , if U = W Γ Γ + max { U , W } , otherwise , Π ( U , W , Γ ) = 0 , if U = W max { U , W } Γ + max { U , W } , otherwise ,
and
M ( U , W , Γ ) = 0 , if U = W max { U , W } Γ , otherwise ,
Then,  ( K , Λ , Π , M , , )  is a NPMS with continuous t-norm  ω ^ h ˘ = ω ^ h ˘  and continuous t-co-norm,  ω ^ f ¯ = max { ω ^ , f ¯ } .
Proof. 
Now, we prove the conditions (v), (x) and (xv) others are obvious.
Let  U = 1 , W = 2 x ˇ = 3 £ = 4  and  ρ = 5 . Then
Λ ( 1 , 5 , Γ + g ˇ + k ˇ + q ˇ ) = Γ + g ˇ + k ˇ + q ˇ Γ + g ˇ + k ˇ + q ˇ + max { 1 , 5 } = Γ + g ˇ + k ˇ + q ˇ Γ + g ˇ + k ˇ + q ˇ + 5 .
On the other hand,
Λ 1 , 2 , Γ = Γ Γ + max { 1 , 2 } = Γ Γ + 2 ,
Λ 2 , 3 , g ˇ = g ˇ g ˇ + max { 2 , 3 } = g ˇ g ˇ + 3 ,
Λ 3 , 4 , k ˇ = k ˇ k ˇ + max { 3 , 4 } = k ˇ k ˇ + 4
and
Λ 4 , 5 , q ˇ = q ˇ q ˇ + max { 4 , 5 } = q ˇ q ˇ + 5 .
i.e.,
Γ + g ˇ + k ˇ + q ˇ Γ + g ˇ + k ˇ + q ˇ + 5 Γ Γ + 2 g ˇ g ˇ + 3 k ˇ k ˇ + 4 q ˇ q ˇ + 5 .
Then it satisfies all  Γ , g ˇ , k ˇ , q ˇ > 0 . Hence,
Λ ( U , ρ , Γ + g ˇ + k ˇ + q ˇ ) Λ U , W , Γ Λ W , x ˇ , g ˇ Λ x ˇ , £ , k ˇ Λ £ , ρ , q ˇ .
Now,
Π ( 1 , 5 , Γ + g ˇ + k ˇ + q ˇ ) = max { 1 , 5 } Γ + g ˇ + k ˇ + q ˇ + max { 1 , 5 } = 5 Γ + g ˇ + k ˇ + q ˇ + 5 .
On the other hand,
Π 1 , 2 , Γ = max { 1 , 2 } Γ + max { 1 , 2 } = 2 Γ + 2 ,
Π 2 , 3 , g ˇ = max { 2 , 3 } g ˇ + max { 2 , 3 } = 3 g ˇ + 3 ,
Π 3 , 4 , k ˇ = max { 3 , 4 } k ˇ + max { 3 , 4 } = 4 k ˇ + 4
and
Π 4 , 5 , q ˇ = max { 4 , 5 } q ˇ + max { 4 , 5 } = 5 q ˇ + 5
i.e.,
5 Γ + g ˇ + k ˇ + q ˇ + 5 max 2 Γ + 2 , 3 g ˇ + 3 , 4 k ˇ + 4 , 5 q ˇ + 5 .
Then it satisfies all  Γ , g ˇ , k ˇ , q ˇ > 0 . Hence,
Π ( U , ρ , Γ + g ˇ + k ˇ + q ˇ ) Π U , W , Γ Π x ˇ , £ , s ^ Π x ˇ , £ , w ^ Π £ , ρ , y ^ .
Now,
M ( 1 , 5 , Γ + g ˇ + k ˇ + q ˇ ) = max { 1 , 5 } Γ + g ˇ + k ˇ + q ˇ = 5 Γ + g ˇ + k ˇ + q ˇ .
On the other hand,
M 1 , 2 , Γ = max { 1 , 2 } Γ = 2 Γ ,
M 2 , 3 , g ˇ = max { 2 , 3 } g ˇ = 3 g ˇ ,
M 3 , 4 , k ˇ = max { 3 , 4 } k ˇ = 4 k ˇ
and
M 4 , 5 , q ˇ = max { 4 , 5 } q ˇ = 5 q ˇ
i.e.,
5 Γ + g ˇ + k ˇ + q ˇ max 2 Γ , 3 g ˇ , 4 k ˇ , 5 q ˇ .
Then it satisfies all  Γ , g ˇ , k ˇ , q ˇ > 0 . Hence,
M ( U , ρ , Γ + g ˇ + k ˇ + q ˇ ) M U , W , Γ M W , x ˇ , g ˇ M x ˇ , £ , k ˇ M £ , ρ , k ˇ .
Hence,  ( K , Λ , Π , M , , )  is a NPMS. □
Remark 1.
The above example satisfies for continuous t-norm  ω ^ f ¯ = min { ω ^ , f ¯ }  and continuous t-co-norm  ω ^ f ¯ = max { ω ^ , f ¯ } .
Definition 8.
Let  ( K , Λ , Π , M , , )  is a NPMS, an open ball is then defined  M ( U , r , Γ )  with center  U , radius  r , 0 < r < 1  and  Γ > 0  as follows:
M ( U , r , Γ ) = { W K : Λ ( U , W , Γ ) > 1 r , Π ( U , W , Γ ) < r , M ( U , W , Γ ) < r } .
Definition 9.
Let  ( K , Λ , Π , M , , )  is a NPMS and  { U β 1 }  be a sequence in  K . Then  { U β 1 }  is called:
(a) 
a convergent if exists  U K  such that
lim β 1 + Λ ( U β 1 , U , Γ ) = 1 , lim β 1 + Π ( U β 1 , U , Γ ) = 0 , lim β 1 + M ( U β 1 , U , Γ ) = 0 , Γ > 0 ,
(b) 
a Cauchy sequence, if for each  f ¯ > 0 , Γ > 0 , exists  β 1 0 N  such that
Λ ( U β 1 , U β 1 + q , Γ ) 1 f ¯ , Π ( U β 1 , U β 1 + q , Γ ) f ¯ , Π ( U β 1 , U β 1 + q , Γ ) f ¯ ,   f o r   a l l   β 1 , m β 1 0 ,
If every Cauchy sequence convergent in  K , then  ( K , Λ , Π , M , , )  is said to be complete NPMS.
Lemma 1.
Let  { U β 1 }  be a Cauchy sequence in NPMS  ( K , Λ , Π , M , , )  such that  U β 1 U m  whenever  m , β 1 N  with  β 1 m . Then the sequence  { U β 1 }  can converge to, at most, one limit point.
Proof. 
Contrarily, suppose that  U β 1 U U β 1 W , and  U W .
Then,  lim β 1 + Λ ( U β 1 , U , Γ ) = 1 lim β 1 + Π ( U β 1 , U , Γ ) = 0 ,
lim β 1 + M ( U β 1 , U , Γ ) = 0 , and  lim β 1 + Λ ( U β 1 , W , Γ ) = 1 ,
lim β 1 + Π ( U β 1 , W , Γ ) = 0 lim β 1 + M ( U β 1 , W , Γ ) = 0 , for all  Γ > 0 . Suppose
Λ ( U , W , Γ ) Λ U , U β 1 , Γ 4 Λ U β 1 , U β 1 + 1 , Γ 4 Λ U β 1 + 1 , U β 1 + 2 , Γ 4 Λ U β 1 + 2 , W , Γ 4 1 1 1 1 , as β 1 + , Π ( U , W , Γ ) Π U , U β 1 , Γ 4 Π U β 1 , U β 1 + 1 , Γ 4 Π U β 1 + 1 , U β 1 + 2 , Γ 4 Π U β 1 + 2 , W , Γ 4 0 0 0 0 , as β 1 + , M ( U , W , Γ ) M U , U β 1 , Γ 4 M U β 1 , U β 1 + 1 , Γ 4 M U β 1 + 1 , U β 1 + 2 , Γ 4 M U β 1 + 2 , W , Γ 4 0 0 0 0 , as β 1 + .
That is  Λ ( U , W , Γ ) 1 1 1 1 = 1 , Π ( U , W , Γ ) 0 0 0 0 = 0  and  M ( U , W , Γ ) 0 0 0 0 = 0 . Hence  U = W , i.e., the sequence converges to at most one limit point. □
Lemma 2.
Let  ( K , Λ , Π , M , , )  is a NPMS. If for some  0 < < 1  and for any  U , W K , Γ > 0 ,
Λ ( U , W , Γ ) Λ U , W , Γ , Π ( U , W , Γ ) Π U , W , Γ , M ( U , W , Γ ) M U , W , Γ
then  U = W .
Proof. 
By (1) follows that
Λ ( U , W , Γ ) Λ U , W , Γ β 1 , Π ( U , W , Γ ) Π U , W , Γ β 1 , M ( U , W , Γ ) M U , W , Γ β 1 , β 1 N , Γ > 0 .
Now
Λ ( U , W , Γ ) lim β 1 + Λ U , W , Γ β 1 = 1 , Π ( U , W , Γ ) lim β 1 + Π U , W , Γ β 1 = 0 , M ( U , W , Γ ) lim β 1 + M U , W , Γ β 1 = 0 , Γ > 0 .
Also, by definition of (iii), (viii), (xiii), i.e.,  U = W . □
Theorem 1.
Suppose  ( K , Λ , Π , M , , )  is a complete NPMS,  ( 0 , 1 )  and assume that
lim Γ + Λ ( U , W , Γ ) = 1 , lim Γ + Π ( U , W , Γ ) = 0 a n d lim Γ + M ( U , W , Γ ) = 0 ,
for all  U , W K  and  Γ > 0 . Let  : K K  be a mapping satisfying
Λ ( U , W , Γ ) Λ ( U , W , Γ ) , Π ( U , W , Γ ) Π ( U , W , Γ ) a n d M ( U , W , Γ ) M ( U , W , Γ ) ,
for all  U , W K  and  Γ > 0 . Then ℘ has a unique fixed point (shortly, ufp).
Proof. 
Consider a point  U 0  of  K  and define a sequence  U β 1  by  U β 1 = β 1 U 0 = U β 1 1 , β 1 N .
By utilising (3) for all  Γ > 0 , we obtain
Λ ( U β 1 , U β 1 + 1 , Γ ) = Λ ( U β 1 1 , U β 1 , Γ ) Λ ( U β 1 1 , U β 1 , Γ ) Λ U β 1 2 , U β 1 1 , Γ Λ U β 1 3 , U β 1 2 , Γ 2 Λ U 0 , U 1 , Γ β 1 1 , Π ( U β 1 , U β 1 + 1 , Γ ) = Π ( U β 1 1 , U β 1 , Γ ) Π ( U β 1 1 , U β 1 , Γ ) Π U β 1 2 , U β 1 1 , Γ Π U β 1 3 , U β 1 2 , Γ 2 Π U 0 , U 1 , Γ β 1 1 .
and
M ( U β 1 , U β 1 + 1 , Γ ) = M ( U β 1 1 , U β 1 , Γ ) M ( U β 1 1 , U β 1 , Γ ) M U β 1 2 , U β 1 1 , Γ M U β 1 3 , U β 1 2 , Γ 2 M U 0 , U 1 , Γ β 1 1 .
We obtain
Λ ( U β 1 , U β 1 + 1 , Γ ) Λ U 0 , U 1 , Γ β 1 1 , Π ( U β 1 , U β 1 + 1 , Γ ) Π U 0 , U 1 , Γ β 1 1 and M ( U β 1 , U β 1 + 1 , Γ ) M U 0 , U 1 , Γ β 1 1 .
Consequently,
Λ ( U β 1 , U β 1 + 2 , Γ ) = Λ ( U β 1 1 , U β 1 + 1 , Γ ) Λ ( U β 1 1 , U β 1 + 1 , Γ ) Λ U β 1 2 , U β 1 , Γ Λ U β 1 3 , U β 1 1 , Γ 2 Λ U 0 , U 2 , Γ β 1 1 , Π ( U β 1 , U β 1 + 2 , Γ ) = Π ( U β 1 1 , U β 1 + 1 , Γ ) Π ( U β 1 1 , U β 1 + 1 , Γ ) Π U β 1 2 , U β 1 , Γ Π U β 1 3 , U β 1 1 , Γ 2 Π U 0 , U 2 , Γ β 1 1 .
and
M ( U β 1 , U β 1 + 2 , Γ ) = M ( U β 1 1 , U β 1 + 1 , Γ ) M ( U β 1 1 , U β 1 + 1 , Γ ) M U β 1 2 , U β 1 , Γ M U β 1 3 , U β 1 1 , Γ 2 M U 0 , U 2 , Γ β 1 1 .
We obtain
Λ ( U β 1 , U β 1 + 2 , Γ ) Λ U 0 , U 2 , Γ β 1 1 , Π ( U β 1 , U β 1 + 2 , Γ ) Π U 0 , U 2 , Γ β 1 1 and M ( U β 1 , U β 1 + 2 , Γ ) M U 0 , U 2 , Γ β 1 1 .
It follows that
Λ ( U β 1 , U β 1 + 3 , Γ ) = Λ ( U β 1 1 , U β 1 + 2 , Γ ) Λ ( U β 1 1 , U β 1 + 2 , Γ ) Λ U β 1 2 , U β 1 + 1 , Γ Λ U β 1 3 , U β 1 , Γ 2 Λ U 0 , U 3 , Γ β 1 1 , Π ( U β 1 , U β 1 + 3 , Γ ) = Π ( U β 1 1 , U β 1 + 2 , Γ ) Π ( U β 1 1 , U β 1 + 2 , Γ ) Π U β 1 2 , U β 1 + 1 , Γ Π U β 1 3 , U β 1 , Γ 2 Π U 0 , U 3 , Γ β 1 1 .
and
M ( U β 1 , U β 1 + 3 , Γ ) = M ( U β 1 1 , U β 1 + 2 , Γ ) M ( U β 1 1 , U β 1 + 2 , Γ ) M U β 1 2 , U β 1 + 1 , Γ M U β 1 3 , U β 1 , Γ 2 M U 0 , U 3 , Γ β 1 1 .
We obtain
Λ ( U β 1 , U β 1 + 3 , Γ ) Λ U 0 , U 3 , Γ β 1 1 , Π ( U β 1 , U β 1 + 3 , Γ ) Π U 0 , U 3 , Γ β 1 1 and M ( U β 1 , U β 1 + 3 , Γ ) M U 0 , U 3 , Γ β 1 1 .
Similarly, for  j = 1 , 2 , 3 , , we obtain
Λ ( U β 1 , U β 1 + 3 j + 1 , Γ ) Λ U 0 , U 3 j + 1 , Γ β 1 1 , Π ( U β 1 , U β 1 + 3 j + 1 , Γ ) Π U 0 , U 3 j + 1 , Γ β 1 1 and M ( U β 1 , U β 1 + 3 j + 1 , Γ ) M U 0 , U 3 j + 1 , Γ β 1 1 ,
Λ ( U β 1 , U β 1 + 3 j + 2 , Γ ) Λ U 0 , U 3 j + 2 , Γ β 1 1 , Π ( U β 1 , U β 1 + 3 j + 2 , Γ ) Π U 0 , U 3 j + 2 , Γ β 1 1 and M ( U β 1 , U β 1 + 3 j + 2 , Γ ) M U 0 , U 3 j + 2 , Γ β 1 1 ,
Λ ( U β 1 , U β 1 + 3 j + 3 , Γ ) Λ U 0 , U 3 j + 3 , Γ β 1 1 , Π ( U β 1 , U β 1 + 3 j + 3 , Γ ) Π U 0 , U 3 j + 3 , Γ β 1 1 and M ( U β 1 , U β 1 + 3 j + 3 , Γ ) M U 0 , U 3 j + 3 , Γ β 1 1 .
By using (4), we obtain for each  j = 1 , 2 , 3 , ,
Λ ( U 0 , U 3 j + 1 , Γ ) Λ U 0 , U 1 , Γ 4 Λ U 0 , U 1 , Γ 4 Λ U 0 , U 1 , Γ 4 Λ U 0 , U 1 , Γ 4 2 Λ U 0 , U 1 , Γ 4 3 Λ U 0 , U 1 , Γ 4 4 Λ U 0 , U 1 , Γ 4 5 Λ U 0 , U 1 , Γ 4 3 j 1 ,
Π ( U 0 , U 3 j + 1 , Γ ) Π U 0 , U 1 , Γ 4 Π U 0 , U 1 , Γ 4 Π U 0 , U 1 , Γ 4 Π U 0 , U 1 , Γ 4 2 Π U 0 , U 1 , Γ 4 3 Π U 0 , U 1 , Γ 4 4 Π U 0 , U 1 , Γ 4 5 Π U 0 , U 1 , Γ 4 3 j 1
and
M ( U 0 , U 3 j + 1 , Γ ) M U 0 , U 1 , Γ 4 M U 0 , U 1 , Γ 4 M U 0 , U 1 , Γ 4 M U 0 , U 1 , Γ 4 2 M U 0 , U 1 , Γ 4 3 M U 0 , U 1 , Γ 4 4 M U 0 , U 1 , Γ 4 5 M U 0 , U 1 , Γ 4 3 j 1 .
Now, from (6), we get
Λ ( U β 1 , U β 1 + 3 j + 1 , Γ ) Λ U 0 , U 3 j + 1 , Γ β 1 1 Λ U 0 , U 1 , Γ 4 β 1 1 Λ U 0 , U 1 , Γ 4 β 1 1 Λ U 0 , U 1 , Γ 4 β 1 Λ U 0 , U 1 , Γ 4 β 1 + 1 Λ U 0 , U 1 , Γ 4 β 1 + 2 Λ U 0 , U 1 , Γ 4 β 1 + 3 Λ U 0 , U 1 , Γ 4 β 1 + 4 Λ U 0 , U 1 , Γ 4 3 j + β 1 2 ,
Π ( U β 1 , U β 1 + 3 j + 1 , Γ ) Π U 0 , U 3 j + 1 , Γ β 1 1 Π U 0 , U 1 , Γ 4 β 1 1 Π U 0 , U 1 , Γ 4 β 1 1 Π U 0 , U 1 , Γ 4 β 1 Π U 0 , U 1 , Γ 4 β 1 + 1 Π U 0 , U 1 , Γ 4 β 1 + 2 Π U 0 , U 1 , Γ 4 β 1 + 3 Π U 0 , U 1 , Γ 4 β 1 + 4 Π U 0 , U 1 , Γ 4 3 j + β 1 2
and
M ( U β 1 , U β 1 + 3 j + 1 , Γ ) M U 0 , U 3 j + 1 , Γ β 1 1 M U 0 , U 1 , Γ 4 β 1 1 M U 0 , U 1 , Γ 4 β 1 1 M U 0 , U 1 , Γ 4 β 1 M U 0 , U 1 , Γ 4 β 1 + 1 M U 0 , U 1 , Γ 4 β 1 + 2 M U 0 , U 1 , Γ 4 β 1 + 3 M U 0 , U 1 , Γ 4 β 1 + 4 M U 0 , U 1 , Γ 4 3 j + β 1 2 .
By using (4) and (5), we obtain for each  j = 1 , 2 , 3 , ,
Λ ( U 0 , U 3 j + 2 , Γ ) Λ U 0 , U 1 , Γ 4 Λ U 0 , U 1 , Γ 4 Λ U 0 , U 1 , Γ 4 Λ U 0 , U 1 , Γ 4 2 Λ U 0 , U 1 , Γ 4 3 Λ U 0 , U 1 , Γ 4 4 Λ U 0 , U 2 , Γ 4 5 Λ U 0 , U 2 , Γ 4 3 j 1 ,
Π ( U 0 , U 3 j + 2 , Γ ) Π U 0 , U 1 , Γ 4 Π U 0 , U 1 , Γ 4 Π U 0 , U 1 , Γ 4 Π U 0 , U 1 , Γ 4 2 Π U 0 , U 1 , Γ 4 3 Π U 0 , U 1 , Γ 4 4 Π U 0 , U 2 , Γ 4 5 Π U 0 , U 2 , Γ 4 3 j 1
and
M ( U 0 , U 3 j + 2 , Γ ) M U 0 , U 1 , Γ 4 M U 0 , U 1 , Γ 4 M U 0 , U 1 , Γ 4 M U 0 , U 1 , Γ 4 2 M U 0 , U 1 , Γ 4 3 M U 0 , U 1 , Γ 4 4 M U 0 , U 2 , Γ 4 5 M U 0 , U 2 , Γ 4 3 j 1 .
Now, from (6), we get
Λ ( U β 1 , U β 1 + 3 j + 2 , Γ ) Λ U 0 , U 3 j + 2 , Γ β 1 1 Λ U 0 , U 1 , Γ 4 β 1 1 Λ U 0 , U 1 , Γ 4 β 1 1 Λ U 0 , U 1 , Γ 4 β 1 Λ U 0 , U 1 , Γ 4 β 1 + 1 Λ U 0 , U 1 , Γ 4 β 1 + 2 Λ U 0 , U 1 , Γ 4 β 1 + 3 Λ U 0 , U 2 , Γ 4 β 1 + 4 Λ U 0 , U 2 , Γ 4 3 j + β 1 2 ,
Π ( U β 1 , U β 1 + 3 j + 2 , Γ ) Π U 0 , U 3 j + 2 , Γ β 1 1 Π U 0 , U 1 , Γ 4 β 1 1 Π U 0 , U 1 , Γ 4 β 1 1 Π U 0 , U 1 , Γ 4 β 1 Π U 0 , U 1 , Γ 4 β 1 + 1 Π U 0 , U 1 , Γ 4 β 1 + 2 Π U 0 , U 1 , Γ 4 β 1 + 3 Π U 0 , U 2 , Γ 4 β 1 + 4 Π U 0 , U 2 , Γ 4 3 j + β 1 2
and
M ( U β 1 , U β 1 + 3 j + 2 , Γ ) M U 0 , U 3 j + 2 , Γ β 1 1 M U 0 , U 1 , Γ 4 β 1 1 M U 0 , U 1 , Γ 4 β 1 1 M U 0 , U 1 , Γ 4 β 1 M U 0 , U 1 , Γ 4 β 1 + 1 M U 0 , U 1 , Γ 4 β 1 + 2 M U 0 , U 1 , Γ 4 β 1 + 3 M U 0 , U 2 , Γ 4 β 1 + 4 M U 0 , U 2 , Γ 4 3 j + β 1 2 .
By using (4) and (5), we obtain for each  j = 1 , 2 , 3 , ,
Λ ( U 0 , U 3 j + 3 , Γ ) Λ U 0 , U 1 , Γ 4 Λ U 0 , U 1 , Γ 4 Λ U 0 , U 1 , Γ 4 Λ U 0 , U 1 , Γ 4 2 Λ U 0 , U 1 , Γ 4 3 Λ U 0 , U 1 , Γ 4 4 Λ U 0 , U 3 , Γ 4 5 Λ U 0 , U 3 , Γ 4 3 j 1 ,
Π ( U 0 , U 3 j + 3 , Γ ) Π U 0 , U 1 , Γ 4 Π U 0 , U 1 , Γ 4 Π U 0 , U 1 , Γ 4 Π U 0 , U 1 , Γ 4 2 Π U 0 , U 1 , Γ 4 3 Π U 0 , U 1 , Γ 4 4 Π U 0 , U 3 , Γ 4 5 Π U 0 , U 3 , Γ 4 3 j 1
and
M ( U 0 , U 3 j + 3 , Γ ) M U 0 , U 1 , Γ 4 M U 0 , U 1 , Γ 4 M U 0 , U 1 , Γ 4 M U 0 , U 1 , Γ 4 2 M U 0 , U 1 , Γ 4 3 M U 0 , U 1 , Γ 4 4 M U 0 , U 3 , Γ 4 5 M U 0 , U 3 , Γ 4 3 j 1 .
Now, from (6), we get
Λ ( U β 1 , U β 1 + 3 j + 3 , Γ ) Λ U 0 , U 3 j + 3 , Γ β 1 1 Λ U 0 , U 1 , Γ 4 β 1 1 Λ U 0 , U 1 , Γ 4 β 1 1 Λ U 0 , U 1 , Γ 4 β 1 Λ U 0 , U 1 , Γ 4 β 1 + 1 Λ U 0 , U 1 , Γ 4 β 1 + 2 Λ U 0 , U 1 , Γ 4 β 1 + 3 Λ U 0 , U 3 , Γ 4 β 1 + 4 Λ U 0 , U 3 , Γ 4 3 j + β 1 2 ,
Π ( U β 1 , U β 1 + 3 j + 3 , Γ ) Π U 0 , U 3 j + 3 , Γ β 1 1 Π U 0 , U 1 , Γ 4 β 1 1 Π U 0 , U 1 , Γ 4 β 1 1 Π U 0 , U 1 , Γ 4 β 1 Π U 0 , U 1 , Γ 4 β 1 + 1 Π U 0 , U 1 , Γ 4 β 1 + 1 Π U 0 , U 1 , Γ 4 β 1 + 3 Π U 0 , U 3 , Γ 4 β 1 + 4 Π U 0 , U 3 , Γ 4 3 j + β 1 2
and
M ( U β 1 , U β 1 + 3 j + 3 , Γ ) M U 0 , U 3 j + 3 , Γ β 1 1 M U 0 , U 1 , Γ 4 β 1 1 M U 0 , U 1 , Γ 4 β 1 1 M U 0 , U 1 , Γ 4 β 1 M U 0 , U 1 , Γ 4 β 1 + 1 M U 0 , U 1 , Γ 4 β 1 + 2 M U 0 , U 1 , Γ 4 β 1 + 3 M U 0 , U 2 , Γ 4 β 1 + 4 M U 0 , U 2 , Γ 4 3 j + β 1 2 .
Using (8)–(16), for each case  β 1 + , we deduce that
lim β 1 + Λ ( U β 1 , U β 1 + i , Γ ) = 1 1 1 = 1 , lim β 1 + Π ( U β 1 , U β 1 + i , Γ ) = 0 0 0 = 0
and
lim β 1 + M ( U β 1 , U β 1 + i , Γ ) = 0 0 0 = 0 .
Which implies that  { U β 1 }  is a Cauchy sequence. Since  ( K , Λ , Π , M , , )  is a complete NPMS, we have
lim β 1 + U β 1 = U .
Now,  U  is a fixed point of , using conditions (v), (x), (xv) and Equation (2), we obtained
Λ ( U , U , Γ ) Λ U , U β 1 , Γ 4 Λ U β 1 , U β 1 + 1 , Γ 4 Λ U β 1 + 1 , U β 1 + 2 , Γ 4 Λ U β 1 + 2 , U , Γ 4 = Λ U , U β 1 , Γ 4 Λ U β 1 1 , U β 1 , Γ 4 Λ U β 1 , U β 1 + 1 , Γ 4 Λ U β 1 + 1 , U , Γ 4 Λ U , U β 1 , Γ 4 Λ U β 1 1 , U β 1 , Γ 4 β 1 2 Λ U β 1 , U β 1 + 1 , Γ 4 β 1 1 Λ U β 1 + 1 , U , Γ 4 1 1 1 1 = 1 as β 1 + ,
Π ( U , U , Γ ) Π U , U β 1 , Γ 4 Π U β 1 , U β 1 + 1 , Γ 4 Π U β 1 + 1 , U β 1 + 2 , Γ 4 Π U β 1 + 2 , U , Γ 4 = Π U , U β 1 , Γ 4 Π U β 1 1 , U β 1 , Γ 4 Π U β 1 , U β 1 + 1 , Γ 4 Π U β 1 + 1 , U , Γ 4 Π U , U β 1 , Γ 4 Π U β 1 1 , U β 1 , Γ 4 β 1 2 Π U β 1 , U β 1 + 1 , Γ 4 β 1 1 Π U β 1 + 1 , U , Γ 4 0 0 0 0 = 0 as β 1 + ,
and
M ( U , U , Γ ) M U , U β 1 , Γ 4 M U β 1 , U β 1 + 1 , Γ 4 M U β 1 + 1 , U β 1 + 2 , Γ 4 M U β 1 + 2 , U , Γ 4 = M U , U β 1 , Γ 4 M U β 1 1 , U β 1 , Γ 4 M U β 1 , U β 1 + 1 , Γ 4 M U β 1 + 1 , U , Γ 4 M U , U β 1 , Γ 4 M U β 1 1 , U β 1 , Γ 4 β 1 2 M U β 1 , U β 1 + 1 , Γ 4 β 1 1 M U β 1 + 1 , U , Γ 4 0 0 0 0 = 0 as β 1 + ,
Hence,  U = U . Let  μ ˜ = μ ˜  for some  μ ˜ K , then
1 Λ ( μ ˜ , U , Γ ) = Λ ( μ ˜ , U , Γ ) Λ μ ˜ , U , Γ = Λ μ ˜ , U , Γ Λ μ ˜ , U , Γ 2 Λ μ ˜ , U , Γ β 1 1 as β 1 + , 0 Π ( μ ˜ , U , Γ ) = Π ( μ ˜ , U , Γ ) Π μ ˜ , U , Γ = Π μ ˜ , U , Γ Π μ ˜ , U , Γ 2 Π μ ˜ , U , Γ β 1 0 as β 1 + ,
and
0 M ( μ ˜ , U , Γ ) = M ( μ ˜ , U , Γ ) M μ ˜ , U , Γ = M μ ˜ , U , Γ M μ ˜ , U , Γ 2 M μ ˜ , U , Γ β 1 0 as β 1 + ,
using by (iii), (viii) and (xiii),  U = μ ˜ . □
Definition 10.
Let  ( K , Λ , Π , M , , )  be a NPMS. A function  : K K  is an NPC (neutrosophic pentagonal contraction) if    0 < < 1 , such that
1 Λ ( P U , P W , Γ ) 1 1 Λ ( U , W , Γ ) 1
Π ( P U , P W , Γ ) Π ( U , W , Γ ) ,
and
M ( P U , P W , Γ ) M ( U , W , Γ ) ,
for all  U , W K  and  Γ > 0 .
Theorem 2.
Let  ( K , Λ , Π , M , , )  be a complete NPMS with  χ : K × K [ 1 , + )  and assume that
lim Γ + M ( U , W , Γ ) = 0 , lim Γ + Π ( U , W , Γ ) = 0 a n d lim Γ + Λ ( U , W , Γ ) = 1 ,
for all  U , W K  and  Γ > 0 . Let  : K K  be a ND-controlled contraction. Furthermore, assume that for an arbitrary  U 0 K , and  β 1 , q N , where  U β 1 = β 1 U 0 = U β 1 1 . Then, ℘ has a ufp.
Proof. 
Suppose  U 0  be a point of  K  and define a sequence  { U β 1 }  by  U β 1 = β 1 U 0 = U β 1 1 , β 1 N . Using by (17)–(19) for all  Γ > 0 , β 1 > q , we deduce
1 Λ ( U β 1 , U β 1 + 1 , Γ ) 1 = 1 Λ ( U β 1 1 , U β 1 , Γ ) 1 1 Λ ( U β 1 1 , U β 1 , Γ ) = Λ ( U β 1 1 , U β 1 , Γ ) .
This implies
1 Λ ( U β 1 , U β 1 + 1 , Γ ) Λ ( U β 1 1 , U β 1 , Γ ) + ( 1 ) 2 Λ ( U β 1 2 , U β 1 1 , Γ ) + ( 1 ) + ( 1 ) .
In this manner, we conclude that
1 Λ ( U β 1 , U β 1 + 1 , Γ ) β 1 Λ ( U 0 , U 1 , Γ ) + β 1 1 ( 1 ) + β 1 2 ( 1 ) + + ( 1 ) + ( 1 ) β 1 Λ ( U 0 , U 1 , Γ ) + ( β 1 1 + β 1 2 + + 1 ) ( 1 ) β 1 Λ ( U 0 , U 1 , Γ ) + ( 1 β 1 ) .
We obtain
1 β 1 Λ ( U 0 , U 1 , Γ ) + ( 1 β 1 ) Λ ( U β 1 , U β 1 + 1 , Γ )
Π ( U β 1 , U β 1 + 1 , Γ ) = Π ( U β 1 1 , U β 1 , Γ ) Π ( U β 1 1 , U β 1 , Γ ) = Π ( U β 1 2 , U β 1 1 , Γ ) 2 Π ( U β 1 2 , U β 1 1 , Γ ) β 1 Π ( U 0 , U 1 , Γ )
and
M ( U β 1 , U β 1 + 1 , Γ ) = M ( U β 1 1 , U β 1 , Γ ) M ( U β 1 1 , U β 1 , Γ ) = M ( U β 1 2 , U β 1 1 , Γ ) 2 M ( U β 1 2 , U β 1 1 , Γ ) β 1 M ( U 0 , U 1 , Γ ) .
It again follows that
1 Λ ( U β 1 , U β 1 + 2 , Γ ) 1 = 1 Λ ( U β 1 1 , U β 1 + 1 , Γ ) 1 1 Λ ( U β 1 1 , U β 1 + 1 , Γ ) = Λ ( U β 1 1 , U β 1 + 1 , Γ ) 1 Λ ( U β 1 , U β 1 + 2 , Γ ) Λ ( U β 1 1 , U β 1 + 1 , Γ ) + ( 1 ) 2 Λ ( U β 1 2 , U β 1 , Γ ) + ( 1 ) + ( 1 ) .
In this manner, we conclude that
1 Λ ( U β 1 , U β 1 + 2 , Γ ) β 1 Λ ( U 0 , U 2 , Γ ) + β 1 1 ( 1 ) + β 1 2 ( 1 ) + + ( 1 ) + ( 1 ) β 1 Λ ( U 0 , U 2 , Γ ) + ( β 1 1 + β 1 2 + + 1 ) ( 1 ) β 1 Λ ( U 0 , U 2 , Γ ) + ( 1 β 1 ) .
We obtain
1 β 1 Λ ( U 0 , U 2 , Γ ) + ( 1 β 1 ) Λ ( U β 1 , U β 1 + 2 , Γ )
Π ( U β 1 , U β 1 + 2 , Γ ) = Π ( U β 1 1 , U β 1 + 1 , Γ ) Π ( U β 1 1 , U β 1 + 1 , Γ ) = Π ( U β 1 2 , U β 1 , Γ ) 2 Π ( U β 1 2 , U β 1 , Γ ) β 1 Π ( U 0 , U 2 , Γ )
and
M ( U β 1 , U β 1 + 2 , Γ ) = M ( U β 1 1 , U β 1 + 1 , Γ ) M ( U β 1 1 , U β 1 + 1 , Γ ) = M ( U β 1 2 , U β 1 , Γ ) 2 M ( U β 1 2 , U β 1 , Γ ) β 1 M ( U 0 , U 2 , Γ ) .
Consequently,
1 Λ ( U β 1 , U β 1 + 3 , Γ ) 1 = 1 Λ ( U β 1 1 , U β 1 + 2 , Γ ) 1 1 Λ ( U β 1 1 , U β 1 + 2 , Γ ) = Λ ( U β 1 1 , U β 1 + 2 , Γ ) .
This implies
1 Λ ( U β 1 , U β 1 + 3 , Γ ) Λ ( U β 1 1 , U β 1 + 2 , Γ ) + ( 1 ) 2 Λ ( U β 1 2 , U β 1 + 1 , Γ ) + ( 1 ) + ( 1 ) .
In this manner, we conclude that
1 Λ ( U β 1 , U β 1 + 3 , Γ ) β 1 Λ ( U 0 , U 3 , Γ ) + β 1 1 ( 1 ) + β 1 2 ( 1 ) + + ( 1 ) + ( 1 ) β 1 Λ ( U 0 , U 3 , Γ ) + ( β 1 1 + β 1 2 + + 1 ) ( 1 ) β 1 Λ ( U 0 , U 3 , Γ ) + ( 1 β 1 ) .
We obtain
1 β 1 Λ ( U 0 , U 3 , Γ ) + ( 1 β 1 ) Λ ( U β 1 , U β 1 + 3 , Γ ) ,
Π ( U β 1 , U β 1 + 3 , Γ ) = Π ( U β 1 1 , U β 1 + 2 , Γ ) Π ( U β 1 1 , U β 1 + 2 , Γ ) = Π ( U β 1 2 , U β 1 + 1 , Γ ) 2 Π ( U β 1 2 , U β 1 + 1 , Γ ) β 1 Π ( U 0 , U 3 , Γ )
and
M ( U β 1 , U β 1 + 3 , Γ ) = M ( U β 1 1 , U β 1 + 2 , Γ ) M ( U β 1 1 , U β 1 + 2 , Γ ) = M ( U β 1 2 , U β 1 + 1 , Γ ) 2 M ( U β 1 2 , U β 1 + 1 , Γ ) β 1 M ( U 0 , U 3 , Γ ) .
Similarly, for  j = 1 , 2 , 3 , , we obtain
1 β 1 Λ ( U 0 , U 3 j + 1 , Γ ) + ( 1 β 1 ) Λ ( U β 1 , U β 1 + 3 j + 1 , Γ ) Π ( U β 1 , U β 1 + 3 j + 1 , Γ ) β 1 Π ( U 0 , U 3 j + 1 , Γ ) and M ( U β 1 , U β 1 + 3 j + 1 , Γ ) β 1 M ( U 0 , U 3 j + 1 , Γ ) , 1 β 1 Λ ( U 0 , U 3 j + 2 , Γ ) + ( 1 β 1 ) Λ ( U β 1 , U β 1 + 3 j + 2 , Γ ) Π ( U β 1 , U β 1 + 3 j + 2 , Γ ) β 1 Π ( U 0 , U 3 j + 2 , Γ ) and M ( U β 1 , U β 1 + 3 j + 2 , Γ ) β 1 M ( U 0 , U 3 j + 2 , Γ ) ,
1 β 1 Λ ( U 0 , U 3 j + 3 , Γ ) + ( 1 β 1 ) Λ ( U β 1 , U β 1 + 3 j + 3 , Γ ) Π ( U β 1 , U β 1 + 3 j + 3 , Γ ) β 1 Π ( U 0 , U 3 j + 3 , Γ ) and M ( U β 1 , U β 1 + 3 j + 3 , Γ ) β 1 M ( U 0 , U 3 j + 3 , Γ ) .
By using (21), we obtain for each  j = 1 , 2 , 3 , . . . . ,
Λ ( U 0 , U 3 j + 1 , Γ ) 1 1 Λ ( U 0 , U 1 , Γ 4 ) 1 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 ) 1 2 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 2 ) 1 3 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 3 ) 1 4 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 4 ) 1 5 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 5 ) 1 6 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 6 ) 1 3 j Λ ( U 0 , U 1 , Γ 4 ) + ( 1 3 j )
Π ( U 0 , U 3 j + 1 , Γ ) Π U 0 , U 1 , Γ 4 Π U 0 , U 1 , Γ 4 2 Π U 0 , U 1 , Γ 4 3 Π U 0 , U 1 , Γ 4 4 Π U 0 , U 1 , Γ 4 5 Π U 0 , U 1 , Γ 4 6 Π U 0 , U 1 , Γ 4 3 j Π U 0 , U 1 , Γ 4
and
M ( U 0 , U 3 j + 1 , Γ ) M U 0 , U 1 , Γ 4 M U 0 , U 1 , Γ 4 2 M U 0 , U 1 , Γ 4 3 M U 0 , U 1 , Γ 4 4 M U 0 , U 1 , Γ 4 5 M U 0 , U 1 , Γ 4 6 M U 0 , U 1 , Γ 4 3 j M U 0 , U 1 , Γ 4 .
Now, from (21), we get
Λ ( U β 1 , U β 1 + 3 j + 1 , Γ ) Λ U 0 , U 3 j + 1 , Γ β 1 1 1 1 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) 1 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 ) 1 2 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 2 ) 1 3 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 3 ) 1 4 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 4 ) 1 5 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 5 ) 1 6 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 6 ) 1 3 j Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 3 j ) ,
Π ( U β 1 , U β 1 + 3 j + 1 , Γ ) Π U 0 , U 3 j + 1 , Γ β 1 1 Π U 0 , U 1 , Γ 4 β 1 1 Π U 0 , U 1 , Γ 4 β 1 1 2 Π U 0 , U 1 , Γ 4 β 1 1 3 Π U 0 , U 1 , Γ 4 β 1 1 4 Π U 0 , U 1 , Γ 4 β 1 1 5 Π U 0 , U 1 , Γ 4 β 1 1 6 Π U 0 , U 1 , Γ 4 β 1 1 3 j Π U 0 , U 1 , Γ 4 β 1 1
and
M ( U β 1 , U β 1 + 3 j + 1 , Γ ) M U 0 , U 3 j + 1 , Γ β 1 1 M U 0 , U 1 , Γ 4 β 1 1 M U 0 , U 1 , Γ 4 β 1 1 2 M U 0 , U 1 , Γ 4 β 1 1 3 M U 0 , U 1 , Γ 4 β 1 1 4 M U 0 , U 1 , Γ 4 β 1 1 5 M U 0 , U 1 , Γ 4 β 1 1 6 M U 0 , U 1 , Γ 4 β 1 1 3 j M U 0 , U 1 , Γ 4 β 1 1 .
By using (21), we obtain for each  j = 1 , 2 , 3 , ,
Λ ( U 0 , U 3 j + 2 , Γ ) 1 1 Λ ( U 0 , U 1 , Γ 4 ) 1 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 ) 1 2 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 2 ) 1 3 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 3 ) 1 4 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 4 ) 1 5 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 5 ) 1 6 Λ ( U 0 , U 2 , Γ 4 ) + ( 1 6 ) 1 3 j Λ ( U 0 , U 1 , Γ 4 ) + ( 1 3 j )
Π ( U 0 , U 3 j + 2 , Γ ) Π U 0 , U 1 , Γ 4 Π U 0 , U 1 , Γ 4 2 Π U 0 , U 1 , Γ 4 3 Π U 0 , U 1 , Γ 4 4 Π U 0 , U 1 , Γ 4 5 Π U 0 , U 1 , Γ 4 6 Π U 0 , U 2 , Γ 4 3 j Π U 0 , U 2 , Γ 4
and
M ( U 0 , U 3 j + 2 , Γ ) M U 0 , U 1 , Γ 4 M U 0 , U 1 , Γ 4 2 M U 0 , U 1 , Γ 4 3 M U 0 , U 1 , Γ 4 4 M U 0 , U 1 , Γ 4 5 M U 0 , U 1 , Γ 4 6 M U 0 , U 2 , Γ 4 3 j M U 0 , U 2 , Γ 4 .
Now, from (21), we get
Λ ( U β 1 , U β 1 + 3 j + 2 , Γ ) Λ U 0 , U 3 j + 2 , Γ β 1 1 1 1 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) 1 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 ) 1 2 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 2 ) 1 3 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 3 ) 1 4 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 4 ) 1 5 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 5 ) 1 6 Λ ( U 0 , U 2 , Γ 4 β 1 1 ) + ( 1 6 ) 1 3 j Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 3 j )
Π ( U β 1 , U β 1 + 3 j + 2 , Γ ) Π U 0 , U 3 j + 2 , Γ β 1 1 Π U 0 , U 1 , Γ 4 β 1 1 Π U 0 , U 1 , Γ 4 β 1 1 2 Π U 0 , U 1 , Γ 4 β 1 1 3 Π U 0 , U 1 , Γ 4 β 1 1 4 Π U 0 , U 1 , Γ 4 β 1 1 5 Π U 0 , U 1 , Γ 4 β 1 1 6 Π U 0 , U 2 , Γ 4 β 1 1 3 j Π U 0 , U 2 , Γ 4 β 1 1
and
M ( U β 1 , U β 1 + 3 j + 2 , Γ ) M U 0 , U 3 j + 2 , Γ β 1 1 M U 0 , U 1 , Γ 4 β 1 1 M U 0 , U 1 , Γ 4 β 1 1 2 M U 0 , U 1 , Γ 4 β 1 1 3 M U 0 , U 1 , Γ 4 β 1 1 4 M U 0 , U 1 , Γ 4 β 1 1 5 M U 0 , U 1 , Γ 4 β 1 1 6 M U 0 , U 2 , Γ 4 β 1 1 3 j M U 0 , U 2 , Γ 4 β 1 1 .
By using (21), we obtain for each  j = 1 , 2 , 3 , ,
Λ ( U 0 , U 3 j + 3 , Γ ) 1 1 Λ ( U 0 , U 1 , Γ 4 ) 1 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 ) 1 2 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 2 ) 1 3 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 3 ) 1 4 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 4 ) 1 5 Λ ( U 0 , U 1 , Γ 4 ) + ( 1 5 ) 1 6 Λ ( U 0 , U 3 , Γ 4 ) + ( 1 6 ) 1 3 j Λ ( U 0 , U 3 , Γ 4 ) + ( 1 3 j )
Π ( U 0 , U 3 j + 3 , Γ ) Π U 0 , U 1 , Γ 4 Π U 0 , U 1 , Γ 4 2 Π U 0 , U 1 , Γ 4 3 Π U 0 , U 1 , Γ 4 4 Π U 0 , U 1 , Γ 4 5 Π U 0 , U 1 , Γ 4 6 Π U 0 , U 3 , Γ 4 3 j Π U 0 , U 3 , Γ 4
and
M ( U 0 , U 3 j + 3 , Γ ) M U 0 , U 1 , Γ 4 M U 0 , U 1 , Γ 4 2 M U 0 , U 1 , Γ 4 3 M U 0 , U 1 , Γ 4 4 M U 0 , U 1 , Γ 4 5 M U 0 , U 1 , Γ 4 6 M U 0 , U 3 , Γ 4 3 j M U 0 , U 3 , Γ 4 .
Now, from (21), we get
Λ ( U β 1 , U β 1 + 3 j + 3 , Γ ) Λ U 0 , U 3 j + 3 , Γ β 1 1 1 1 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) 1 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 ) 1 2 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 2 ) 1 3 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 3 ) 1 4 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 4 ) 1 5 Λ ( U 0 , U 1 , Γ 4 β 1 1 ) + ( 1 5 ) 1 6 Λ ( U 0 , U 3 , Γ 4 β 1 1 ) + ( 1 6 ) 1 3 j Λ ( U 0 , U 3 , Γ 4 β 1 1 ) + ( 1 3 j ) ,
Π ( U β 1 , U β 1 + 3 j + 3 , Γ ) Π U 0 , U 3 j + 3 , Γ β 1 1 Π U 0 , U 1 , Γ 4 β 1 1 Π U 0 , U 1 , Γ 4 β 1 1 2 Π U 0 , U 1 , Γ 4 β 1 1 3 Π U 0 , U 1 , Γ 4 β 1 1 4 Π U 0 , U 1 , Γ 4 β 1 1 5 Π U 0 , U 1 , Γ 4 β 1 1 6 Π U 0 , U 3 , Γ 4 β 1 1 3 j Π U 0 , U 3 , Γ 4 β 1 1
and
M ( U β 1 , U β 1 + 3 j + 3 , Γ ) M U 0 , U 3 j + 3 , Γ β 1 1 M U 0 , U 1 , Γ 4 β 1 1 M U 0 , U 1 , Γ 4 β 1 1 2 M U 0 , U 1 , Γ 4 β 1 1 3 M U 0 , U 1 , Γ 4 β 1 1 4 M U 0 , U 1 , Γ 4 β 1 1 5 M U 0 , U 1 , Γ 4 β 1 1 6 M U 0 , U 3 , Γ 4 β 1 1 3 j M U 0 , U 3 , Γ 4 β 1 1 .
Using (22)–(29), for each case  β 1 + , we deduce
lim β 1 + Λ ( U β 1 , U β 1 + q , Γ ) = 1 1 1 = 1 , lim β 1 + Π ( U β 1 , U β 1 + q , Γ ) = 0 0 0 = 0 ,
and
lim β 1 + M ( U β 1 , U β 1 + q , Γ ) = 0 0 0 = 0 .
It follows that  { U β 1 }  is a Cauchy sequence. Since  ( K , Λ , Π , M , , )  be a complete NPMS, there exists
lim β 1 + U β 1 = U .
Since (v), (x) and (xv), we get
1 Λ ( U β 1 , U , Γ ) 1 1 Λ ( U β 1 , U , Γ ) 1 = Λ ( U β 1 , U , Γ ) 1 Λ ( U β 1 , U , Γ ) + ( 1 ) Λ ( U β 1 , U , Γ ) .
By the above inequality, we have
Λ ( U , U , Γ ) Λ U , U β 1 , Γ 4 Λ U β 1 , U β 1 + 1 , Γ 4 Λ U β 1 + 1 , U β 1 + 2 , Γ 4 Λ U β 1 + 2 , U , Γ 4 Λ U , U β 1 , Γ 4 Λ U β 1 1 , U β 1 , Γ 4 Λ U β 1 , U β 1 + 1 , Γ 4 Λ U β 1 + 1 , U , Γ 4 Λ U , U β 1 , Γ 4 1 β 1 1 Λ ( U β 1 1 , U β 1 , Γ 4 ) + ( 1 β 1 1 ) 1 β 1 Λ ( U β 1 , U β 1 + 1 , Γ 4 ) + ( 1 β 1 ) 1 Λ ( U β 1 + 1 , U , Γ 4 ) + ( 1 ) 1 1 1 1 = 1 as β 1 + ,
Π ( U , U , Γ ) Π U , U β 1 , Γ 4 Π U β 1 , U β 1 + 1 , Γ 4 Π U β 1 + 1 , U β 1 + 2 , Γ 4 Π U β 1 + 2 , U , Γ 4 Π U , U β 1 , Γ 4 Π U β 1 1 , U β 1 , Γ 4 Π U β 1 , U β 1 + 1 , Γ 4 Π U β 1 + 1 , U , Γ 4 Π U , U β 1 , Γ 4 β 1 1 Π U β 1 1 , U β 1 , Γ 4 β 1 Π U β 1 , U β 1 + 1 , Γ 4 Π U β 1 + 1 , U , Γ 4 0 0 0 0 = 0 as β 1 +
and
M ( U , U , Γ ) M U , U β 1 , Γ 4 M U β 1 , U β 1 + 1 , Γ 4 M U β 1 + 1 , U β 1 + 2 , Γ 4 M U β 1 + 2 , U , Γ 4 M U , U β 1 , Γ 4 M U β 1 1 , U β 1 , Γ 4 M U β 1 , U β 1 + 1 , Γ 4 M U β 1 , U , Γ 4 M U , U β 1 , Γ 4 β 1 1 M U β 1 1 , U β 1 , Γ 4 β 1 M U β 1 , U β 1 + 1 , Γ 4 M U β 1 , U , Γ 4 0 0 0 0 = 0 as β 1 + .
Hence,  U = U . Let  μ ˜ = μ ˜  for some  μ ˜ K , then
1 Λ ( U , μ ˜ , Γ ) 1 = 1 Λ ( U , μ ˜ , Γ ) 1 1 Λ ( U , μ ˜ , Γ ) 1 < 1 Λ ( U , μ ˜ , Γ ) 1 ,
which is a contradiction.
Π ( U , μ ˜ , Γ ) = Π ( U , μ ˜ , Γ ) Π ( U , μ ˜ , Γ ) < Π ( U , μ ˜ , Γ ) ,
which is a contradiction and
M ( U , μ ˜ , Γ ) = M ( U , μ ˜ , Γ ) M ( U , μ ˜ , Γ ) < M ( U , μ ˜ , Γ ) ,
which is a contradiction. Therefore, we obtain  Λ ( U , μ ˜ , Γ ) = 1 , Π ( U , μ ˜ , Γ ) = 0  and  M ( U , μ ˜ , Γ ) = 0 , hence,  U = μ ˜ . □
Example 2.
Let  K = [ 0 , 1 ] . Define  Λ , Π , M : K × K × ( 0 , + ) [ 0 , 1 ]  as
Λ ( U , W , Γ ) = Γ Γ + | U W | , Π ( U , W , Γ ) = | U W | Γ + | U W | , M ( U , W , Γ ) = | U W | Γ .
Then,  ( K , Λ , Π , M , , )  is a complete NPMS with continuous t-norm and t-co-norm, i.e.,  ω ^ h ˘ = ω ^ h ˘  and  ω ^ h ˘ = max { ω ^ , h ˘ } .
Define  : K K  by  ( U ) = 1 3 U 11  and set  [ 1 2 , 1 ) , then
Λ ( U , W , Γ ) = Λ 1 3 U 11 , 1 3 W 11 , Γ = Γ Γ + | 1 3 U 11 1 3 W 11 | = Γ Γ + | 3 U 3 W | 11 Γ Γ + | U W | 11 = 11 Γ 11 Γ + | U W | Γ Γ + | U W | = Λ ( U , W , Γ ) ,
Π ( U , W , Γ ) = Π 1 3 U 11 , 1 3 W 11 , Γ = | 1 3 U 11 1 3 W 11 | Γ + | 1 3 U 11 1 3 W 11 | = | 3 U 3 W | 11 Γ + | 3 U 3 W | 11 = | 3 U 3 W | 11 Γ + | 3 U 3 W | | U W | 11 Γ + | U W | | U W | Γ + | U W | = Π ( U , W , Γ )
and
M ( U , W , Γ ) = M 1 3 U 11 , 1 3 W 11 , Γ = | 1 3 U 11 1 3 W 11 | Γ = | 3 U 3 W | 11 Γ = | 3 U 3 W | 11 Γ | U W | 11 Γ | U W | Γ = M ( U , W , Γ ) .
As a result, all of Theorem 1 criteria are satisfied, and 0 is the only fixed point for ℘.

4. Applications

4.1. Application to Fredholm Integral Equation

Let  K = C ( [ 𝚥 , δ ] , R )  be the set of real value continuous functions on  [ 𝚥 , δ ] .
Consider the integral equation:
U ( ) = ( ) + 𝚥 δ ( , κ ) U ( ) ς κ for , κ [ 𝚥 , δ ] ,
where  ( κ )  is a fuzzy function of  κ [ 𝚥 , δ ] > 0  and  : C ( [ 𝚥 , δ ] × R ) R + . Define  Λ Π  and  M  by means of
Λ ( U ( ) , W ( ) , Γ ) = sup [ 𝚥 , δ ] Γ Γ + | U ( ) W ( ) | U , W K and Γ > 0 , Π ( U ( ) , W ( ) , Γ ) = 1 sup [ 𝚥 , δ ] Γ Γ + | U ( ) W ( ) | U , W K and Γ > 0 ,
and
M ( U ( ) , W ( ) , Γ ) = sup [ 𝚥 , δ ] | U ( ) W ( ) | Γ U , W K and Γ > 0 ,
by continuous t-norm and continuous t-co-norm define by  ω ^ h ˘ = ω ^ · h ˘  and  ω ^ h ˘ = max { ω ^ , h ˘ } . Then  ( K , Λ , Π , M , , )  is a complete NPMS. Suppose that  | ( , κ ) U ( ) ( , κ ) W ( ) | | U ( ) W ( ) |  for  U , W K , 0 < < 1  and  , κ [ 𝚥 , δ ] . Let  ( , κ ) ( 𝚥 δ d κ ) < 1 . Then Equation (30) has a unique solution.
Proof. 
Define  : K K  by
U ( ) = ( ) + 𝚥 δ ( , κ ) U ( ) ς κ , for all , κ [ 𝚥 , δ ] .
Now, for all  U , W K , we deduce
Λ ( U ( ) , W ( ) , Γ ) = sup [ 𝚥 , δ ] Γ Γ + | U ( ) W ( ) | = sup [ 𝚥 , δ ] Γ Γ + | ( ) + 𝚥 δ ( , κ ) U ( ) ς κ ( ) 𝚥 δ ( , κ ) U ( ) ς κ | = sup [ 𝚥 , δ ] Γ Γ + | 𝚥 δ ( , κ ) U ( ) ς κ 𝚥 δ ( , κ ) U ( ) ς κ | = sup [ 𝚥 , δ ] Γ Γ + | ( , κ ) U ( ) ( , κ ) W ( ) | ( 𝚥 δ ς κ ) sup [ 𝚥 , δ ] Γ Γ + | U ( ) W ( ) | Λ ( U ( ) , W ( ) , Γ ) ,
Π ( U ( ) , W ( ) , Γ ) = 1 sup [ 𝚥 , δ ] Γ Γ + | U ( ) W ( ) | = 1 sup [ 𝚥 , δ ] Γ Γ + | ( ) + 𝚥 δ ( , κ ) U ( ) ς κ ( ) 𝚥 δ ( , κ ) U ( ) ς κ | = 1 sup [ 𝚥 , δ ] Γ Γ + | 𝚥 δ ( , κ ) U ( ) ς κ 𝚥 δ ( , κ ) U ( ) ς κ | = 1 sup [ 𝚥 , δ ] Γ Γ + | ( , κ ) U ( ) ( , κ ) W ( ) | ( 𝚥 δ ς κ ) 1 sup [ 𝚥 , δ ] Γ Γ + | U ( ) W ( ) | Π ( U ( ) , W ( ) , Γ ) ,
and
M ( U ( ) , W ( ) , Γ ) = sup [ 𝚥 , δ ] | U ( ) W ( ) | Γ = sup [ 𝚥 , δ ] | ( ) + 𝚥 δ ( , κ ) U ( ) ς κ ( ) 𝚥 δ ( , κ ) U ( ) ς κ | Γ = sup [ 𝚥 , δ ] | 𝚥 δ ( , κ ) U ( ) ς κ 𝚥 δ ( , κ ) U ( ) ς κ | Γ = sup [ 𝚥 , δ ] | ( , κ ) U ( ) ( , κ ) W ( ) | ( 𝚥 δ ς κ ) Γ sup [ 𝚥 , δ ] | U ( ) W ( ) | Γ M ( U ( ) , W ( ) , Γ ) ,
As a result, has a ufp and all of the requirements of Theorem 1 are fulfilled. It is obvious that the Equation (30) has only one solution. □
Example 3.
Consider the non-linear integral equation.
U ( ) = | cos | + 1 11 0 1 κ U ( κ ) ς κ ,   f o r   a l l   κ [ 0 , 1 ] .
Then it has a solution in  K .
Proof. 
Let  : K K  be defined by
U ( ) = | cos | + 1 11 0 1 κ U ( κ ) ς κ ,
and set  ( , κ ) U ( ) = 1 11 κ U ( κ )  and  ( , κ ) W ( ) = 1 11 κ W ( κ ) , where  U , W K , and  , κ [ 0 , 1 ] . Then we obtain
| ( , κ ) U ( ) ( , κ ) W ( ) | = | 1 11 κ U ( κ ) 1 11 κ W ( κ ) | = κ 11 | U ( κ ) W ( κ ) | | U ( κ ) W ( κ ) | .
Furthermore, see that  1 11 0 1 κ ς κ = 1 11 ( 1 ) 2 2 ( 0 ) 2 2 = 1 11 = 1 , where  = 1 11 . Then, it follows that all criteria of the above application are easily verified and the above problem has a solution in  K . □

4.2. Application to Fractional Differential Equations

In order to start, we need to review some basic definitions from the theory of fractional calculus.
For a function  U C [ 0 , 1 ] , the Reiman-Liouville fractional derivative of order  > 0  is given by
1 F ( β 1 ) d β 1 d β 1 0 U ( 𝚥 ) d 𝚥 ( 𝚥 ) β 1 + 1 = D U ( ) ,
For as long as the right hand side is pointwise defined on  [ 0 , 1 ] [ ]  is the integer portion of the number  , F  is the Euler gamma function.
Consider the following fractional differential equation
𝚥 D χ U ( ) + f ( , U ( ) ) = 0 , 1 0 , 2 χ > 1 ; U ( 0 ) = U ( 1 ) = 0 ,
where  f  is a continuous function from  [ 0 , 1 ] × R  to  R  and  𝚥 D χ  represents the Caputo fractional derivative of order  χ  and it is defined by
𝚥 D χ = 1 F ( β 1 χ ) 0 U β 1 ( 𝚥 ) d 𝚥 ( 𝚥 ) χ β 1 + 1 .
The given fractional differential Equation (31) is equivalent
U ( ) = 0 1 Υ ( , 𝚥 ) f ( , U ( 𝚥 ) ) d 𝚥 ,
for all  U Y  and  [ 0 , 1 ] , where
Υ ( , 𝚥 ) = [ ( 1 𝚥 ) ] χ 1 ( 𝚥 ) χ 1 F ( χ ) , 0 𝚥 1 , [ ( 1 𝚥 ) ] χ 1 F ( χ ) , 0 𝚥 1 .
Let  C ( [ 0 , 1 ] , R ) = K  be the space of all continuous functions defined on  [ 0 , 1 ] . Define  Λ Π  and  M  by means of
Λ ( U ( ) , W ( ) , Γ ) = sup [ 0 , 1 ] Γ Γ + | U ( ) W ( ) | ,   for   all   U , W K and Γ > 0 , Π ( U ( ) , W ( ) , Γ ) = 1 sup [ 0 , 1 ] Γ Γ + | U ( ) W ( ) | ,   for   all   U , W K and Γ > 0
and
M ( U ( ) , W ( ) , Γ ) = sup [ 0 , 1 ] | U ( ) W ( ) | Γ ,   for   all   U , W K and Γ > 0 ,
with continuous t-norm and continuous t-co-norm define by  ω ^ h ˘ = ω ^ · h ˘  and  ω ^ h ˘ = max { ω ^ , h ˘ } . Then  ( K , Λ , Π , M , , )  is a complete NPMS.
Theorem 3.
Consider the nonlinear fractional differential Equation (31). Let us assume that the following claims are true:
(i)
there exist  [ 0 , 1 ]  and  U , W C ( [ 0 , 1 ] , R )  such that
| f ( , U ) f ( , W ) | | U ( ) W ( ) | ;
(ii)
sup [ 0 , 1 ] 0 1 Υ ( , 𝚥 ) ς < 1 .
Then the fractional differential Equation (31) has a unique solution in  K .
Proof. 
Let us consider the function  : K K  defined by
K U ( ) = 0 1 Υ ( , 𝚥 ) f ( , U ( 𝚥 ) ) d 𝚥 .
It is obvious that  U *  is a solution to the problem (31) if  U *  is a fixed point of .
Now, for all  U , W K , we deduce
Λ ( U ( ) , W ( ) , Γ ) = sup [ 0 , 1 ] Γ Γ + | U ( ) W ( ) | = sup [ 0 , 1 ] Γ Γ + | 0 1 Υ ( , 𝚥 ) f ( , U ( 𝚥 ) ) d 𝚥 0 1 Υ ( , 𝚥 ) f ( , W ( 𝚥 ) ) d 𝚥 | = sup [ 0 , 1 ] Γ Γ + 0 1 Υ ( , 𝚥 ) | f ( , U ( 𝚥 ) ) f ( , W ( 𝚥 ) ) | d 𝚥 sup [ 0 , 1 ] Γ Γ + | U ( ) W ( ) | Λ ( U ( ) , W ( ) , Γ ) ,
Π ( U ( ) , W ( ) , Γ ) = 1 sup [ 0 , 1 ] Γ Γ + | U ( ) W ( ) | = 1 sup [ 0 , 1 ] Γ Γ + | 0 1 Υ ( , 𝚥 ) f ( , U ( 𝚥 ) ) d 𝚥 0 1 Υ ( , 𝚥 ) f ( , W ( 𝚥 ) ) d 𝚥 | = 1 sup [ 0 , 1 ] Γ Γ + 0 1 Υ ( , 𝚥 ) | f ( , U ( 𝚥 ) ) f ( , W ( 𝚥 ) ) | d 𝚥 1 sup [ 0 , 1 ] Γ Γ + | U ( ) W ( ) | Π ( U ( ) , W ( ) , Γ )
and
M ( U ( ) , W ( ) , Γ ) = sup [ 0 , 1 ] | U ( ) W ( ) | Γ = sup [ 0 , 1 ] | 0 1 Υ ( , 𝚥 ) f ( , U ( 𝚥 ) ) d 𝚥 0 1 Υ ( , 𝚥 ) f ( , W ( 𝚥 ) ) d 𝚥 | Γ = sup [ 0 , 1 ] 0 1 Υ ( , 𝚥 ) | f ( , U ( 𝚥 ) ) f ( , W ( 𝚥 ) ) | d 𝚥 Γ sup [ 0 , 1 ] | U ( ) W ( ) | Γ M ( U ( ) , W ( ) , Γ ) .
As a result, has a ufp and all of Theorem 1 requirements are satisfied. It implies that there is only one solution to the Equation (30). □

5. Conclusions

We proposed the idea of neutrosophic pentagonal MS in this study and proved new varieties of fixed-point theorems. By applying a new methodology to an application based on the literature, we have shown that it outperforms our results.

Author Contributions

Conceptualization, G.M., P.S., Z.D.M., A.A. and N.M.; formal analysis, Z.D.M., A.A. and N.M.; writing—original draft preparation, G.M., P.S., Z.D.M., A.A. and N.M.; writing—review and editing, G.M., P.S., Z.D.M., A.A. and N.M.; funding acquisition, A.A. and N.M. All authors have and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

The authors A. Aloqaily and N. Mlaiki thank Prince Sultan University for paying the APC and for the support from the TAS research lab.

Conflicts of Interest

The authors declare no conflict of interest.

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Mani, G.; Subbarayan, P.; Mitrović, Z.D.; Aloqaily, A.; Mlaiki, N. Solving Some Integral and Fractional Differential Equations via Neutrosophic Pentagonal Metric Space. Axioms 2023, 12, 758. https://doi.org/10.3390/axioms12080758

AMA Style

Mani G, Subbarayan P, Mitrović ZD, Aloqaily A, Mlaiki N. Solving Some Integral and Fractional Differential Equations via Neutrosophic Pentagonal Metric Space. Axioms. 2023; 12(8):758. https://doi.org/10.3390/axioms12080758

Chicago/Turabian Style

Mani, Gunaseelan, Poornavel Subbarayan, Zoran D. Mitrović, Ahmad Aloqaily, and Nabil Mlaiki. 2023. "Solving Some Integral and Fractional Differential Equations via Neutrosophic Pentagonal Metric Space" Axioms 12, no. 8: 758. https://doi.org/10.3390/axioms12080758

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