1. Introduction
The theory of fixed point has been studiedfor a long time and the fundamental concept linked to this theory is the concept of Banach’s contraction [
1]. It is well known for its simple nature and for being an applicable model forstudying the solutions of integral equations, differential equations, BVP problems, and many other problems in nonlinear analysis. Since then, many researchers have scientifically developed important extensions and generalized notions of metric space and the contractive map. Interesting scientific research is related to different abstract general metric settings and finding appropriate contractive conditions.
We emphasize some of the maingeneralizations that provide great developments to the fixed point theory, such as the concepts of
metric [
2,
3] and
metric-like [
4]; many scientists have contributed to this theory with papers and essential results, and furthermore we can list references [
5,
6,
7,
8,
9,
10,
11,
12,
13,
14]. In 2012, Samet defined
admissible mapping [
15], and further triangular
admissible mapping [
16]. In the same year, Wardowski [
17] established the notion of
contraction by using an auxiliary function under some imposed conditions, and later in 2018 introduced the notion of
contraction [
18]. The classes of
contraction and
contraction, revisited simultaneously with
admissible mapping, are still a main focus and have been considered in the literature widely, and many fixed point theorems have beenpresented in metric space,
metric and
metric-like space (for short
m.l.s), and other spaces. For a valuable work anddetails on these notions, see [
19,
20,
21,
22,
23,
24,
25,
26,
27,
28]. Later, Karapinar [
29] came up with the notion of interpolative contraction, ongoing together with
hybrid contractions, as defined by M. Sh. Shagari [
30]. In this regard, and to become familiar with more accurate information, interested readers can browse references [
31,
32,
33,
34,
35,
36].
In the presented paper, the general types of contractions and order hybrid contractions are introduced, as a variant of Wardowski contractions and contractions in the setting of m.l.s. By using these classes of contractions, we set up general new results which expand, generalize, and unify the repertoire for fixedpoint results beyond the types of interpolative and hybrid contractions discussed so far.
2. Preliminaries
First, let us obtain an understanding of the preliminary base concepts and notations.
Definition 1 ([4]). Let be a nonempty set and a parameter . A mapping is called a metric-like if for all the following conditions are satisfied: The pair is called a metric-like space. (
m.l.s for short). Definition 2 ([4]). Let be a m.l.s with parameter and let be any sequence in and . Then, the following applies:
- (a)
converges to , iff ;
- (b)
is Cauchy sequence in
, iff
exists and is finite;
- (c)
is complete
m.l.s, iff for every Cauchy sequence
in
, there exists
such that
.
Definition 3 ([4]). Let be a m.l.s with parameter and a function . We say that the function is continuous if for each sequence the sequence whenever as that is, if yields .
In a m.l.s, it is remarked that if , then the limit of the sequence is unique if it exists.
Definition 4 ([15]). Let be a non-empty set. Let and be given functions. We say that is an admissible mapping if implies that for all .
Definition 5 ([10]). Let be a m.l.s, and be given mappings, and let be an arbitrary constant. We can say that is an admissible mapping if which implies for all .
For illustrative examples belonging to this category of
admissible functions, one can search in references [
7,
10].
Definition 6. Let be a m.l.s with parameter , , . Then, the function satisfies admissible property; if a sequence with and and then there exists a subsequence of with and for all and .
Definition 7. Let be a m.l.s with parameter , , . Then, the function fulfills the unique property, if for all fixed points of , we have where .
Lemma 1 ([4]). Let be a m.l.s with parameter , and suppose that is convergent to and . Then, for each , we have Lemma 2 ([7]). Let be a m.l.s with parameter . Then, the following applies:
- (a)
implies
- (b)
If for ,
, then we have
;
- (c)
implies
.
Lemma 3 ([9]). Let be a sequence in a complete –m.l.s with parameter , such that If , then there exists and sequences and of natural numbers with (positive integers) such that and . 3. Results
In this section, we introduce the new notion of general types of contractions in the setting of m.l.s that can be seen as a new form of linear and nonlinear contractions involving classical contractions, Wardowski type contractions, and interpolative and hybrid contractions.
Before proposing our definitions and theorems, we will use these formal notations:
is the set of all continuous functions where , satisfying the conditions:
- ➢
is non-decreasing withrespect to each variable;
- ➢
for
Definition 8. Let be a m.l.s with parameter and . The self-mapping on is named a generalized contraction, if there exist such thatfor all
with
and
where
for some
.
Remark 1. Some specific evidence of this definition ispointed out: aking the function as constant function, we derived a generalized contraction. his definition extends and generalizes some definitions in [6,7,18,19,25,35]. By taking the function as a constant function or we can obtain other new definitions in the same metric structure. Also, this definition respectively holds validity in metric settings where obtaining: Generalized , contractions. Theorem 1. Let be a complete m.l.s with parameter and a self-mapping satisfying the conditions:
- C1
there exists
with
- C2
is
admissible mapping and satisfies
admissible property;
- C3
is a generalized
contraction.
Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. Since C1 is satisfied,
exists such that
. We construct the sequence
via aniterative equation
for all
. Then,
and since
is
admissible it follows
, so inductively it can be concluded that
. Now, if we suppose that
exists with
, then the proof is completed. Therefore, we assume
for all
(it means
). Applying inequality (1) and property of
, we have
where
If we assume that
, then
And, from inequality (2), it follows that
The inequality (3) generates
which is a contradiction. Therefore, we have for all
:
Hence,
is a decreasing sequence of nonnegative numbers. So, there exists
such that
as
. If we suppose that
, then using (5) and the property of
, Equation (3) can be written as
If we take the limit along (6) as
, then
which is a contradiction. Thus, we state that
.
Next, we show that
. Then, we suppose the contrary, that is,
. Then, according to Lemma 3,
exists, as well as sequences
and
of positive integers with
such that
Since
, we apply condition (1) as
where
By taking the limit superior in Equation (10) and using Lemma 3, and result (7), we obtain
Taking the upper limit as
along (9) and using (11), we have
Hence, the acquired inequality
is a contradiction since
and
. Thus,
Hence,
is a Cauchy sequence in
. Since it is complete, there is some
, such that the sequence
is convergent to
. Thus, according to def 2/(c) and (13), we have
Since
satisfies the
admissible property, there exists a subsequence
of
such that
for all
. Again, by using (1) and the property of
, we have
where
Taking the limit superior as
, in
and in view of Lemma 1, we obtain
Again, taking the upper limit as
in (15), and according to Lemma 1, the result (17) and property of
, it follows that
Hence, since
, the inequality (18) implies that
and so
. Therefore,
is a fixed point for which
If we suppose that
and
are two fixed points of
where
and
with
, that is
, then using (19) and the property of
, for
, we have
Since,
satisfies the
unique property, then
, and from condition (1) and the above inequality, we have
and (21) leads to a contradiction that implies
. Therefore,
. □
Corollary 1. Let be a m.l.s with parameter and the mappings . If there exist such that fulfill the condition andfor all with and where for .
Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. Take the function as constant . □
Example 1. Let be a complete m.l.s with a coefficient where , with for all . Consider the maps: , , respectively, given by For
with
,
and
, that is,
is
admissible mapping. Consider
as
,
as
, and
as
, and then in the case of
, we have
In the case of
and
, we have
Obviously, the conditions of Theorem 1 are confirmed and has as a unique fixed point. Already, this theorem is not applicable in the frame of metric space and metric space, as we can see from the additional dates.
For
,
using the usual metric
(and
), and taking
, any increasing function
, and any function
, we have
Hence, we can say that the
and
contractive condition is not satisfied. Also, we can remark the same in a b-metric space with b-metric
where
Corollary 2. Let be a m.l.s with parameter and a self-mapping If there exist such thatfor all
with , and some , where for some .
Then, has a unique fixed point in .
Proof. Take the function □
In the following theorem, we will use another function to help cover rational expressions in the set .
Theorem 2. Let be a m.l.s with parameter and . If there exist such that the following conditions are met:
- C1
There exists
with ;
- C2
is admissible mapping and satisfies admissible property;
- C3
for all
with and where for some , and is a continuous function with for all . Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. Repeating the same process as in the previous theorem, for
with
; build the iterative sequence
by
such that
for all
The proof is clear in the case that
exists, with
.Assuming that
for all
taking into account (1) for
, we have
where
The result is the same as in Theorem 1, and the proof goes along the same lines.□
Corollary 3. Let be a m.l.s with parameter and . If there exist such that satisfy theconditions andfor all with and .
Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. This comes from Theorem 2 by taking □
Corollary 4. Let be a m.l.s with parameter and . If there exist such that satisfy the conditions andfor all with and .
Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. The proof is consideredcompletedwhenthe substitution in Corollary 3 with as is made.□
Corollary 5. Let be a m.l.s with parameter and . If there exist such that satisfy the conditions andfor all with and .
Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. This comes from Theorem 1 by taking as with . □
Corollary 6. Let be a m.l.s with parameter and . If there exist such that satisfy the conditions andfor all with and Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. The proof is completed by taking as and the function in Theorem 2.□
Corollary 7. Let be a m.l.s with parameter and . If there exist such that satisfy the condition andfor all with and Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. It comes from Theorem 2 by taking as with
and the function □
Remark 2. The above corollaries 6; 7 correspond to the Dass-Gupta and Jaggi contractions. They are the generalization and extension of the theorems in [6,10,35,36,37]. In the following part, we generalize some previous definitions that have to do with interpolation and hybrid contractions in metric and generalized metric spaces. The theorems established for these classes of contractions, in the sequel and in the published literature, are a common important focus of Theorems 1 and 2.
Definition 9. Let be a m.l.s with parameter and . The self-mapping on is named aHardy–Rogers type interpolative contraction, if there exist and with such thatfor all
with
and
where Definition 10. Let be a m.l.s with parameter and . The self-mapping on is named a Hardy–Rogers order hybrid contraction if there exist such thatfor all
with and such that where Remark 3. Taking , consequently, we obtain the corresponding definitions in metric spaces. Taking we derive the order hybrid contraction. Taking we naturally obtain the order hybrid contraction. Definition 10 generates an order interpolative contraction and order contraction. The general Definition 8 generates the above Definitions 9 and 10, and all classical contractions for certain types of and all classical contractions. It integrates many new forms of contractions that have been recently defined.
Theorem 3. Let be a m.l.s with parameter and . If is an interpolative Hardy–Rogers type contraction, and conditions hold, then has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. It is derived from Theorem 1 by taking as , where and . □
Theorem 4. Let be a m.l.s with parameter , and . If there exist such that satisfy the conditions andfor all with , and .
Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. It comes from Theorem 1 by taking as , where . □
Theorem 5. Let be a m.l.s with parameter and . If there exist such that hold conditions andfor all with , and .
Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. It is a special case of Theorem 1 when we take
as
□
Theorem 6. Let be a m.l.s with parameter , and mappings , if the following conditions are satisfied:
- C1
There exists
with
- C2
is admissible mapping and satisfies admissible property;
- C3
is a generalized order hybrid contraction.
Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. And, we take functions as ; where with .
Theorem 7. Let be a m.l.s with parameter and . If there exist such that satisfy the conditions andfor all
with
and such that where Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. The proof is considered completed using Theorem 1, if we take
and define
where
□
Theorem 8. Let be a m.l.s with parameter , and , . If there exist such that satisfy the condition andfor all
with and and such that where Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. We take Theorem 2
,
and define
□
Remark 4. Theorem 8 can be considered as new result for Jaggi order hybrid contractions and Dass and Gupta type order hybrid contractions extended in m.l.s; they are also a special case of generalized contractions.
Theorem 9. Let be a m.l.s with parameter , and , . If there exist such that satisfy the condition andfor all
with and and such that where Then, has a fixed point in . Moreover, it is unique if satisfies the unique property.
Proof. We take Theorem 1 with the function
and define
□
Remark 5. In Definition 9 and also Theorem 3
- -
By taking where , with and we obtain Definition 2 and, respectively, Theorem 4 in [
31]
in the version; so, our result is an extension, generalization, and new result in the framework of metric and b-metric-like-spaces. - -
By taking where with and , we obtain Definition 3 and, respectively, Theorem 4 in [
34]
in the version. - -
By taking we obtain some theorems in [
8].
- -
By taking where is non decreasing function on such that for and for each , also with , we obtain Definition 3 and, respectively, Theorem 1 in [
32]
, in the version. - -
In view of the implicit relation set , our definitions and, respectively, the stated Theorems have a general character and unifying power.
- -
The same consequences are present for Definition 10 and related theorems.