Abstract
We undertake this study with the objective of introducing certain control functions in the contractive condition to prove fixed-point theorems in the framework of complex-valued bipolar metric spaces. The incorporation of control functions broadens the applicability of the contractive condition. This approach yields key results consistent with previous studies. In support of our results, we offer two insightful examples that demonstrate the concepts discussed. Additionally, we present the notion of interpolative contraction in this new and generalized metric space and prove fixed-point theorems for non-self mappings. To demonstrate the application of our approach, we reproduce key findings from several established studies in the field.
Keywords:
control functions; complex-valued bipolar metric space; interpolative contraction; fixed point MSC:
47H10; 54H25
1. Introduction
Fixed-point (FP) theory, a cornerstone of mathematical analysis, delves into the fascinating world of self-mapping functions. It seeks to identify elements within a set that remain unchanged when the function is applied. This seemingly simple concept has profound implications across various branches of mathematics, including differential equations, optimization, and functional analysis. Antón-Sancho [1,2,3] investigated the existence and properties of FPs within the space of principal -bundles defined over a compact algebraic curve. FPs in the space of vector bundles defined over a compact Riemann surface subjected to various automorphisms are also identified and analyzed. The foundation of FP theory is arguably laid by the Banach contraction principle (BCP) [4]. This powerful theorem, established by Stefan Banach in 1922, guarantees the existence of a unique FP for a contraction mapping within a complete metric space (CMS). It provides a clear and elegant method to analyze iterative processes and has become a cornerstone for numerous extensions and applications. Building upon the BCP, Kannan [5] introduced his influential FP theorem in 1968. This theorem broadened the applicability of FP theory by relaxing the contractive condition, allowing for a wider range of functions to possess fixed points. Further enriching the landscape, Reich [6] presented his FP theorem. This theorem ingeniously integrated the BCP and Kannan’s result, offering a more general framework for establishing FPs under specific conditions. The quest for more versatile FP theorems continued with Fisher’s contribution [7]. His FP theorem incorporated rational expressions within the contractive condition, leading to a wider range of functions satisfying the necessary criteria for fixed points. Subsequently, Khan [8] introduced another rational expression within the contractive condition, further expanding the applicability of FP theory. Following the above two results, Jaggi [9] incorporated a new rational expression into the contractive condition of the Banach principle. This refinement, known as Jaggi’s FP theorem, demonstrates the continuous evolution of FP theory with ever-expanding tools for analyzing self-mapping functions.
The fruitful exploration of FPs in these theorems is facilitated by the rich theory of CMSs, offering a robust framework for analyzing distances. Metric spaces have numerous applications across various scientific fields, like mathematics, computer science, physics, chemistry, and biology. This wide applicability has led researchers to explore extensions and generalizations of the concept. Azam et al. [10] began the idea of complex-valued metric spaces (CVMSs) by replacing the real number range with complex numbers. Their work established the existence of common FPs for certain mappings using Fisher’s contractions. Subsequently, Rouzkard et al. [11] extended this result by incorporating a rational term into the contraction condition. Sintunavarat et al. [12] further generalized these findings by introducing variable-dependent control functions. Sitthikul et al. [13] contributed by proving common FP theorems within the framework of CVMSs. Ahmad et al. [14] demonstrated the appropriateness of their findings by establishing the existence of solutions to a second-order differential equation. In classical MSs and CVMSs, we typically consider the distance between elements within a single set. This naturally leads to the question of how to define and compute the distance between elements in two different sets. Such issues arise in various fields of mathematics. To address these issues, Mutlu et al. [15] unveiled the concept of bipolar metric spaces (bipMSs). This new notion has facilitated the advancement of FP theory, particularly in developing Banach’s and Kannan’s FP results. Later on, Paul et al. [16] established FP results for contractions involving Jaggi’s and Khan’s rational expressions in the framework of bipMSs. Kishore et al. [17] presented applications of their outcomes in the domains of integral equations and homotopy theory. Extensive research has been conducted on the existence of FPs within the framework of bipMSs (see [18,19,20] and references therein). Recently, Siva [21] put forward the notion of complex-valued bipolar metric spaces (CVbipMSs) and proved FP theorems for contravariant mappings under rational contractions.
This research leverages the concept of CVbipMSs to obtain FP results for rational contractions containing certain control functions. Our approach successfully recovers several established findings documented in the literature. Some non-trivial examples to support our findings are also furnished. Additionally, we present the notion of interpolative contraction in CVbipMSs and prove FP theorems for non-self mappings.
2. Preliminaries
To establish a solid groundwork for the ensuing discussions, we present essential definitions, notations, and preliminary results in this section. Pioneering the field, the Banach contraction principle [4] is formulated as follows:
Theorem 1
([4]). Let be a CMS and , satisfying
for all , and for some ; then, has a unique fixed point (UFP).
In a significant contribution to the field, Kannan [5] established the subsequent theorem:
Theorem 2
([5]). Let be a CMS and , satisfying
for all , and for some ; then, has a UFP.
Reich [6] subsequently unified the Banach contraction principle and Kannan’s fixed-point result through the following approach.
Theorem 3
([6]). Let be a CMS and , satisfying
for all , and for some , with ; then, has a UFP.
Leveraging the Banach contraction principle, Fisher [7] formulated a refined contractive condition incorporating a novel rational expression. This approach yields the next result.
Theorem 4
([7]). Let be a self-mapping on the CMS . We investigate the following contractive condition for
for all , and for some , with ; then, has a UFP.
In an extension of the Banach contraction principle, Jaggi [9] incorporated a new rational expression into the contractive condition, achieving the following result.
Theorem 5
([9]). Consider a continuous self-map defined on a CMS . Suppose fulfills the following contractive condition:
for all , , and for some , with ; then, has a UFP.
In 1976, Khan [8] introduced a novel rational expression within the contractive condition, leading to the following result.
Theorem 6
([8]). Let be a CMS and , satisfying
for all , with ; then, has a UFP.
Azam et al. [10] put forward the idea of the CVMS in such a fashion.
Definition 1
([10]). If is a complex number, then
- x represents the real part of z;
- y represents the imaginary part of z;
- i is the imaginary unit, defined as the square root of (i.e., ).
Now, let. The set is equipped with a partial order ≾ defined by
It follows that
if one of these assertions is satisfied:
Definition 2
([10]). Let and be a mapping satisfying
- (i)
- and ⇔
- (ii)
- (iii)
∀. Then, is said to be a CVMS.
Example 1
([10]). Let and Define by
Then, is a CVMS.
Mutlu et al. [15] originated the thought of bipMSs in such a manner.
Definition 3
([15]). Let and and let , satisfying
- ()
- ,
- ()
- , if
- ()
- ,
for all
Then, is called a bipMS.
Example 2
([15]). Let Ω and ℧ be two classes of all singleton and compact subsets of Define by
for and ; then, is a complete bipMS.
Definition 4
([15]). Let and be two bipMSs. A mapping is said to be a covariant mapping if and Similarly, a mapping is called a contravariant mapping if and
The covariant mapping will be represented by the symbol and the contravariant mapping by .
3. Complex-Valued Bipolar Metric Space
This section establishes the foundation for our research by presenting the idea of a CVbipMS. It includes the definitions of covariant and contravariant mappings, as well as the relevant lemmas. Very recently, Siva [21] defined the notion of the CVbipMS in the following way.
Definition 5
([21]). Let and and be a function fulfilling the following conditions:
- (cvb1)
- and ⟺ for
- (cvb2)
- for all
- (cvb3)
for all and
Then, the triple is called a CVbipMS.
Remark 1
([21]). Let be a CVbipMS. Then, the space is said to be disjoint if If the space is referred to as a joint. The sets Ω and ℧ are referred to as the left and right poles of , respectively.
Example 3
([21]). Let Ω be the set of functions such that and ℧ be the set of all complex numbers Now, we define by
where Then, is a CVbipMS.
Lemma 1
([21]). Let be a CVbipMS. A left sequence converges to a right point iff and also, a right sequence converges to a left point if and only ifas
Lemma 2
([21]). Let be a CVbipMS. When a central point serves as a sequence’s limit, the central point acts as the sequence’s unique limit.
Lemma 3
([21]). Let be a CVbipMS. If a left sequence converges to and a right sequence converges to , thenas
Definition 6
([21]). Let and be two CVbipMSs. The mapping is a mapping.
(i) If and then is said to be a covariant mapping from to We use to represent covariant mappings.
(ii) If and then is said to be contravariant mapping from to We express the contravariant mappings as
Definition 7
([21]). Let be a CVbipMS.
(i) A sequence ( on is reputed to be bisequence on
(ii) Assuming that sequences () and () converge, their corresponding bisequence ( also converges. If both () and () converge to the same limit, the bisequence ( is termed biconvergent.
(iii) If for each there exists such that a bisequence ( in a CVbipMS is often described as a Cauchy, if for every ∃ such that for
Lemma 4
([21]). Let be a CVbipMS and let be a bisequence. Then, is a Cauchy iff as where
4. Main Results
The primary goal of this section is to establish the core findings of our research. We begin by proving a foundational proposition that serves as a cornerstone for subsequent results.
Proposition 1.
Let and and Define the bisequence {} on as
for all
Assume that there exists satisfying
for all ( Then,
for all ( and
Proof.
Let ( and Then, we have
Similarly, we have
□
Theorem 7.
Let be a complete CVbipMS and let . If there exist mappings such that
(a) and
and
and
(b)
(c)
for all and then has a UFP in .
Proof.
Let and Define the bisequence {} on as
Now, by (1), we have
By proposition (1), we have
This implies that
which further implies that
Similarly, by (1), we have
By proposition (1), we have
which implies that
Set Then, by (3) and (4), it is easy to see that
Similarly, we have
for all For (if we have
Similarly, if then we have
Now, taking the limit as we obtain Thus, is a Cauchy in By using the completeness of the CVbipMS , we find that biconverges to a limit point Therefore, Hence, as implies as by using Lemma (3). Now, by (1), we have
By proposition (1), we have
which implies
Taking the limit as we obtain
which is possible only if Hence, Thus, has a fixed point. Now, if is another fixed point of then implies that Then,
which is a contradiction, except □
Example 4.
Let and Define by
for all Then, is a complete CVbipMS. Define by and Then, is a contravariant mapping. Define by
Consequently, hypotheses (a) and (b) of Theorem 7 are satisfied by these control functions, and the mapping fulfills inequality 1. Thus, there exists a UFP 0 of the mapping
Corollary 1.
Let be a complete CVbipMS and let . If there exist mappings such that
(a) and
and
(b)
(c)
for all then has a UFP.
Proof.
Define as in Theorem 7. □
Corollary 2.
Let be a complete CVbipMS and let . If there exist mappings such that
(a) and
and
(b)
(c)
for all then has a UFP.
Proof.
Define as in Theorem 7. □
Remark 2.
If in the above corollary, then CVbipMS is reduced to a CVMS. This allows us to directly recover a result established by Sitthikul et al. [13].
Remark 3.
If and we define by and in the above corollary, we directly arrive at the central finding established by Sintunavarat et al. [12].
Remark 4.
If and we define by and in the above corollary, we essentially achieve the conditions of Azam et al. [10], leading directly to their main result.
Corollary 3
([21]). Let be a complete CVbipMS and let . If there exist the constants with such that
for all then has a UFP.
Proof.
Define by and in Theorem 7. □
Theorem 8.
Let be a complete CVbipMS and let be continuous. If there exist mappings such that
(a) and
and
and
(b)
(c)
for all with , then has a UFP in .
Proof.
Let and Define the bisequence {} on as
Now, by (1), we have
By proposition (1), we have
This implies that
which further implies that
Similarly, by (8), we have
By proposition (1), we have
which implies that
which implies
Set Then, by (10) and (11), it is easy to see that
Similarly, we have
for all By following the same procedure as outlined in Theorem 7, we can demonstrate that forms a Cauchy in By using the completeness of , we find that biconverges to a point So, as Hence, as Also, as Since is continuous,
Thus, has an FP. Now, if is another FP of then implies that Then,
which leads to a contradiction. Hence, □
Corollary 4.
Let be a complete CVbipMS and let be continuous. If there exist some constants such that and
for all with , then has a UFP in .
Proof.
Define as and in Theorem 8. □
Remark 5.
If we set in the given Definition 5, then the CVbipMS is reduced to a bip-MS, directly yielding a key result established by Paul et al. [16].
Corollary 5.
Let be a complete CVbipMS and let be continuous. If there exist mappings such that
(a) and
and
(b)
(c)
for all with , then has a UFP in .
Proof.
Define as in Theorem 8. □
Corollary 6.
Let be a complete CVbipMS and let be continuous. If there exist some constants such that and
for all with , then has a UFP in .
Remark 6.
Setting the imaginary component of z to zero in Definition 5 reduces the CVbipMS to a bipMS, yielding the result of Paul et al. [16] as a corollary.
Theorem 9.
Let be a complete CVbipMS and let be continuous. If there exist mappings such that
(a) and
and
and
(b)
(c)
for all then has a UFP in .
Proof.
Let and Define the bisequence {} on as
Now, by (14), we have
By proposition (1), we have
This implies that
which further implies that
Similarly, by (14), we have
By proposition (1), we have
which implies that
Set Then, by (16) and (17), it is easy to see that
Similarly, we have
for all By applying the same method used in Theorem 7, we can establish that the bisequence is a Cauchy in is complete, so as Consequently, as Hence, as Also, as Since is continuous,
Thus, has an FP. Now, if is another FP of then implies that Then,
which would normally be contradictory, except □
Corollary 7.
Let be a complete CVbipMS and let be continuous. If there exist some constants such that and
for all then has a UFP in .
Remark 7.
Setting the imaginary component of z to zero in Definition 5 reduces the CVbipMS to a bipMS, yielding the result of Paul et al. [16] as a corollary.
Definition 8.
Let be a CVbipMS. A mapping is said to be an interpolative contraction if there exist and such that
for all where
Theorem 10.
Let be a complete CVbipMS and the mapping be an interpolative contraction; then, has an FP in
Proof.
Let and Define the bisequence {} on as
for each positive integer Now, by (20), we have
which implies that
which further implies that
Suppose that Then, from (21), we have
which is a contradiction because Thus, we we conclude that for all Thus, is a non-increasing sequence, and by inequality (21), there exists a nonnegative constant such that Then, the inequality (21) yields
Similarly, by (1), we have
which implies that
which further implies that
Suppose that Then, from (23), we have
which is a contradiction because Thus, we we conclude that for all Thus, is a non-increasing sequence, and by inequality (23), we conclude that there exists a nonnegative constant such that Then, inequality (23) yields
Then, by (22) and (24), it is easy to see that
Similarly, we have
for all For (if we have
Similarly, if then we have
Now, taking the limit as we obtain Thus, forms a Cauchy in Given that is complete, biconverges to a point Consequently, and Therefore, as , which implies as by using Lemma (3). Now, by (1), we have
which implies
Taking the limit as we obtain Hence, Thus, has an FP. □
Example 5.
Let and Define by
for all then, is a complete CVbipMS. Define by for all . We can therefore verify that all the requirements of Theorem 10 hold true for and and that has an FP. Clearly, 6 is the FP of .
5. Conclusions and Future Directions
In this manuscript, we have introduced some precise control functions in contractive inequalities and proved the FPs of contravariant mappings in the situation of a CVbipMS. As a consequence of our chief outcomes, we derived some well-known results from the literature, including the core achievements of Azam et al. [10], Sintunavarat et al. [12], Sitthikul et al. [13], Paul et al. [16], and Siva [21]. Some illustrative examples are also provided to verify the authenticity of the accomplished theorem. We also put forward the idea of interpolative contraction in the background of CVbipMSs and established an FP theorem for contravariant mappings.
Building on our current findings, future research will delve deeper into the intriguing behavior of FPs for set-valued functions in the intricate foundation of CVbipMSs. Furthermore, the proposed contractions can be extended to encompass a broader class of metric spaces beyond CVbipMSs. The potential applications of these results can be investigated in the context of fractional differential equations and even integral equations. Additionally, efficient computational algorithms can be designed to tackle FP problems stemming from the proposed contractions.
Author Contributions
Conceptualization, A.E.S.; Methodology, A.E.S.; Formal analysis, J.A.; Investigation, A.E.S.; Resources, J.A.; Writing—original draft, A.E.S.; Writing—review & editing, A.E.S.; Visualization, J.A.; Supervision, J.A.; Project administration, J.A.; Funding acquisition, J.A. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Data Availability Statement
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.
Conflicts of Interest
The authors declare that they have no conflicts of interest.
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