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.
Keywords:
neutrosophic metric space; neutrosophic pentagonal metric space; fixed point results; integral equation; fractional differential equation MSC:
47H10; 54H25
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 -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 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 -admissible and --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 be a binary operation is said to be a continuous triangle norm if:
- (1)
- ;
- (2)
- ★ is continuous;
- (3)
- ;
- (4)
- , ∀ ;
- (5)
- If and , ∀ , then .
Definition 2
([19]). Let be a binary operation is said to be a continuous triangle co-norm if:
- (1)
- , ∀ ;
- (2)
- • is continuous;
- (3)
- , ∀ ;
- (4)
- , ∀ ;
- (5)
- If and , with , then .
Definition 3
([24]). Let be given two non-comparable functions, if satisfies axioms:
- (a)
- iff ;
- (b)
- ;
- (c)
- ;
∀ , then, is known to be a double controlled MS (shortly, DCMS).
Definition 4
([25]). Let and be known non-comparable functions. And ★ is a continuous t-norm also Λ be a fuzzy set on is said to be fuzzy double controlled metric on , ∀ if:
- (i)
- ;
- (ii)
- ∀, ⇔;
- (iii)
- ;
- (iv)
- ;
- (v)
- is continuous on left.
Then, is known to be a fuzzy DCMS.
Definition 5
([20]). Let . Let ★, • are the continuous t-norm, continuous t-co-norm respectively, and be fuzzy sets on . If fullfils all and :
- (I)
- ;
- (II)
- ;
- (III)
- ;
- (IV)
- ;
- (V)
- ;
- (VI)
- is a non-decreasing function of and ;
- (VII)
- ;
- (VIII)
- ;
- (IX)
- ;
- (X)
- ;
- (XI)
- is a non-increasing function of and ,
Then, is an intuitionistic fuzzy ♭-MS.
Definition 6
([21]). Let , ★, • are the continuous t-norm, continuous t-co-norm respectively, and are neutrosophic sets (shortly, N-sets) on is known to be a neutrosophic metric on , if for all , the following axioms are fulfilled:
- (1)
- ;
- (2)
- ;
- (3)
- ∀, ⇔;
- (4)
- ;
- (5)
- ;
- (6)
- is continuous and ;
- (7)
- ;
- (8)
- ∀, ⇔;
- (9)
- ;
- (10)
- ;
- (11)
- is continuous and ;
- (12)
- ;
- (13)
- ∀, ⇔;
- (14)
- ;
- (15)
- ;
- (16)
- is continuous and ;
- (17)
- If , then ;
Then, 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 and function be non-comparable, ★, • are the continuous t-norm, continuous t-co-norm respectively, and be N-sets on is known to be a neutrosophic pentagonal metric on , if for any and all distinct , the following axioms are fulfilled:
- (i)
- ;
- (ii)
- ;
- (iii)
- ∀, ⇔;
- (iv)
- ;
- (v)
- ;
- (vi)
- is continuous and ;
- (vii)
- ;
- (viii)
- ∀, ⇔;
- (ix)
- ;
- (x)
- ;
- (xi)
- is continuous and ;
- (xii)
- ;
- (xiii)
- ∀, ⇔;
- (xiv)
- ;
- (xv)
- ;
- (xvi)
- is continuous and ;
- (xvii)
- If , then and .
Then, is said to be a NPMS.
Example 1.
Let . Define as
and
Then, is a NPMS with continuous t-norm and continuous t-co-norm, .
Proof.
Now, we prove the conditions (v), (x) and (xv) others are obvious.
Let , , and . Then
On the other hand,
and
i.e.,
Then it satisfies all . Hence,
Now,
On the other hand,
and
i.e.,
Then it satisfies all . Hence,
Now,
On the other hand,
and
i.e.,
Then it satisfies all . Hence,
Hence, is a NPMS. □
Remark 1.
The above example satisfies for continuous t-norm and continuous t-co-norm .
Definition 8.
Let is a NPMS, an open ball is then defined with center , radius and as follows:
Definition 9.
Let is a NPMS and be a sequence in . Then is called:
- (a)
- a convergent if exists such that
- (b)
- a Cauchy sequence, if for each , exists such thatIf every Cauchy sequence convergent in , then is said to be complete NPMS.
Lemma 1.
Let be a Cauchy sequence in NPMS such that whenever with . Then the sequence can converge to, at most, one limit point.
Proof.
Contrarily, suppose that , , and .
Then, , ,
, and ,
, , for all . Suppose
That is and . Hence , i.e., the sequence converges to at most one limit point. □
Lemma 2.
Let is a NPMS. If for some and for any ,
then .
Proof.
Theorem 1.
Suppose is a complete NPMS, and assume that
for all and . Let be a mapping satisfying
for all and . Then ℘ has a unique fixed point (shortly, ufp).
Proof.
Consider a point of and define a sequence by .
By utilising (3) for all , we obtain
and
We obtain
Consequently,
and
We obtain
It follows that
and
We obtain
Similarly, for , we obtain
By using (4), we obtain for each
and
Now, from (6), we get
and
By using (4) and (5), we obtain for each
and
Now, from (6), we get
and
By using (4) and (5), we obtain for each
and
Now, from (6), we get
and
Using (8)–(16), for each case , we deduce that
and
Which implies that is a Cauchy sequence. Since is a complete NPMS, we have
Now, is a fixed point of ℘, using conditions (v), (x), (xv) and Equation (2), we obtained
and
Hence, . Let for some , then
and
using by (iii), (viii) and (xiii), . □
Definition 10.
Let be a NPMS. A function is an NPC (neutrosophic pentagonal contraction) if , such that
and
for all and .
Theorem 2.
Let be a complete NPMS with and assume that
for all and . Let be a ND-controlled contraction. Furthermore, assume that for an arbitrary , and , where . Then, ℘ has a ufp.
Proof.
Suppose be a point of and define a sequence by . Using by (17)–(19) for all , we deduce
This implies
In this manner, we conclude that
We obtain
and
It again follows that
In this manner, we conclude that
We obtain
and
Consequently,
This implies
In this manner, we conclude that
We obtain
and
Similarly, for , we obtain
By using (21), we obtain for each
and
Now, from (21), we get
and
By using (21), we obtain for each
and
Now, from (21), we get
and
By using (21), we obtain for each
and
Now, from (21), we get
and
Using (22)–(29), for each case , we deduce
and
It follows that is a Cauchy sequence. Since be a complete NPMS, there exists
Since (v), (x) and (xv), we get
By the above inequality, we have
and
Hence, . Let for some , then
which is a contradiction.
which is a contradiction and
which is a contradiction. Therefore, we obtain and , hence, . □
Example 2.
Let . Define as
Then, is a complete NPMS with continuous t-norm and t-co-norm, i.e., and .
Define by and set , then
and
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 be the set of real value continuous functions on .
Consider the integral equation:
where is a fuzzy function of , and . Define , and by means of
and
by continuous t-norm and continuous t-co-norm define by and . Then is a complete NPMS. Suppose that for and . Let . Then Equation (30) has a unique solution.
Proof.
Define by
Now, for all , we deduce
and
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.
Then it has a solution in .
Proof.
Let be defined by
and set and , where , and . Then we obtain
Furthermore, see that , where . Then, it follows that all criteria of the above application are easily verified and the above problem has a solution in . □
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 , the Reiman-Liouville fractional derivative of order is given by
For as long as the right hand side is pointwise defined on , is the integer portion of the number is the Euler gamma function.
Consider the following fractional differential equation
where is a continuous function from to and represents the Caputo fractional derivative of order and it is defined by
The given fractional differential Equation (31) is equivalent
for all and , where
Let be the space of all continuous functions defined on . Define , and by means of
and
with continuous t-norm and continuous t-co-norm define by and . Then is a complete NPMS.
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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