Fixed Point Approximation for Suzuki Generalized Nonexpansive Mapping Using B(δ, μ) Condition ()
1. Introduction
Let
be a Banach space and
. For a mapping
, a point
is said to be a fixed point if
. Also, a mapping
is said to be nonexpansive if
We will refer to the set of natural numbers as
and the set of real numbers as
throughout the whole study and the set of all fixed points of
is referred by
. If a mapping
then it is said to be quasi-nonexpansive mappings if
and
and
. Browder [1] (also refer [2] [3]), Gohde [4], and Kirk [5] independently scrutinised the significance of fixed points for nonexpansive mappings in the framework of Banach spaces. They exemplified that if
is a nonempty, closed, bounded, and convex subset of a uniformly convex Banach space, then each nonexpansive mapping
seems to have at least one fixed point. Several other researchers have examined an amount of generalisations of nonexpansive mappings in recent decades. Suzuki introduced a new class of mappings (weaker than nonexpansiveness and stronger than quasi-nonexpansiveness) known as Suzuki generalised nonexpansive mappings, which is really a consequence on mappings regarded as Condition (C), and successfully obtained several other convergence and existence findings for these kinds of mappings in [6]. A mapping
is said to satisfy Condition (C) (oftentimes Suzuki generalised nonexpansive) if
for each
.
Suzuki illustrated that Condition (C) is relatively weak than nonexpansion and stronger than quasi-nonexpansion. Falset et al. [7] introduced two new classes of generalised nonexpansive mappings that are wider than those satisfying the (C) condition whilst also retaining their fixed point attributes in 2011. We established a novel category of mappings in this paper that is relatively large than the class order to satisfy the Condition (C). Including some examples, we scrutinise the existence of fixed points for this category of mapping. First, we’ll go over some key concepts. Every nonexpansive mapping evidently ensures the Condition (C).
Suzuki [6] [7] exemplified that Condition (C) is much more general than nonexpansiveness through the following example.
Example: [8] Define a mapping
by
(1)
It is worth noting that
appeases Condition (C), however it is not nonexpansive. In 2018, Patir et al. [8] recently standardised the conception of Condition (C), and is as continues to follow:
[8] Consider a
and
, a mapping
such that
is known to achieve
condition if there is an existence of
and
satisfying the condition
in such a manner that
,
signifies
Remark: It is observable that a mapping with Condition (C) achieves the
condition.
Example: [8] Define a mapping
by
(2)
Here,
satisfies
condition, but not Condition (C).
It is instinctual to investigate the processing of fixed points for known existence results, and that’s not an easy process. The Picard iteration process is being used in the Banach contraction mapping criterion. The Picard iteration process is as follows:
and is used to the approximate unique fixed point. Mann [9], Ishikawa [10], S [11], Noor [12], Abbas [13], Thakur et al. [14], and so forth are other excellently iteration techniques. The convergence rate is absolutely essential for an iteration process to be favoured over the other iteration process. Rhoades [15] suggested that the Mann iteration process converges faster than that of the Ishikawa iterative procedure for significantly decreasing function as well as the Ishikawa iterative model is better for significantly increasing function than that of the Mann iterative procedure. The renowned Mann [9] and Ishikawa [10] iteration procedures are described as follows:
(3)
where
.
(4)
where
. The following iteration approach, known as S iteration, was established by Agarwal et al. [11] in 2007:
(5)
where
. They observed that for the class of contraction mappings, the speed of convergence of the (5) iteration process is much like the Picard iteration and speedier than the Mann iteration process. Thakur et al. [14] used a modified iterative algorithm, which was described as follows:
(6)
where
.
They asserted that (6) is significantly faster than Picard, Mann, Ishikawa, Agarwal, Noor, and Abbas iteration algorithms for the class of Suzuki generalised nonexpansive mappings through numerical examples.
Recently in 2018, Ullah and Arshad [16] introduced
iteration process:
(7)
where
. They contended that iteration (8) had a faster rate of convergence than that of the other iteration methods.
Question. Is it feasible to establish an iteration process that has a faster convergence rate than that of the iteration processes (7)?
As a response, we propose the AK' iterative approach, which is a newer version, and is as follows:
(8)
where
. In this way, we approximate fixed points of mapping which satisfies condition
. We compare the convergence rate of our novel AK' iteration approach to current faster iteration schemes using a numerical example.
2. Numerical Example
In this section, an example is given to support the assertion that AK' iteration scheme converges faster than the
and S iteration scheme.
Example Let
and
. Let
be mapping defined as
. Obviously
is an invariant point of
. Let
and
,
and
. The iterative values for
are given in Table 1 where as the Study of AK’ for initial value
for function
with
and
for AK',
and S iteration processes is studied in Table 2.
In compared to conventional iteration processes, the proposed AK' iterative model clearly converges faster to the fixed point of
.
Table 1. Study of AK' for initial value
.
Table 2. Study of AK' for initial value
for function
.
3. Preliminaries
In this section, we give some preliminaries. Let
be a Banach space and
be a nonempty closed convex subset of
. Let
be a bounded sequence in
. For
, set
The asymptotic radius of
relative to
is given by
The asymptotic centre of
relative to
is the set
It’s also commonly acknowledged that
encompasses essentially one point in a uniformly convex Banach space. Furthermore, when
is nonempty and convex in the case when
is weakly compact and convex, see [2] [3] [16] [17] [18] also refer [19] - [29] for fixed point based literature.
So, here are a few effective approaches and consequences. Let
is a Banach space, it is known as uniformly convex if for each
, there is an existence of
in such a manner that for every
,
Definition [17] A Banach space
is said to have Opial’s property if for each sequence
in
which weakly converges to
and for every
, it satisfies the following
Examples of Banach spaces satisfying this condition are Hilbert spaces and all
spaces (
).
Definition [17] Let
be subset of a Banach space
. Let
. A Banach space
is said to have satisfy Condition (C) if there is a function
satisfying
and
such that
(9)
, where
represents distance of x from
.
Definition [7] If
is a closed convex and bounded subset of Banach space
, and a self-mapping
on
is nonexpansive, then there exists a sequence
in
such that
. Such a sequence is called almost fixed point sequence for
.
We now list some basic facts about Suzuki generalized nonexpansive mappings, which can be found in [6]. The following useful Lemma can be found in [18].
Lemma 1 Let
be a uniformly convex Banach space and
for every
. If
and
are two sequences in
such that
,
and
for some
then,
. also,let
be a Suzuki generalized nonexpansive mapping defined on a subset
of a Banach space
with the Opial property. If a sequence
converges weakly to z and
, then I-
is democlosed at zero.
The following Lemma gives many examples of mappings with
condition.
Lemma 2 [8] Let
be subset of a Banach space
. Let
be a self mapping on
. if
satisfies Condition (C), then
satisfies
condition.
Lemma 3 [8] Let
be subset of a Banach space
. Let
satisfies
condition. if
is a fixed point of
, then for each
Theorem 4 Let
be a Banach space.
be a nonempty subset of
and
be a mapping satisfies condition
. if
be such that
1)
converges weakly to
;
2)
.
Then,
.
Proposition 5 Let
be a Banach space.
be a nonempty subset of
and
be a mapping satisfies condition
on
, then
and
1)
2) at least one of the following (a) and b)) holds:
a)
b)
condition a) implies
and condition b) implies
.
3)
Then,
.
Lemma 6 Let
be a uniformly convex Banach space and
. If
and
are two sequences in
such that
,
, and
for some
then
.
4. Convergence Analysis
In this section, we study the convergence analysis of AK' iteration scheme for which following Lemma plays a significant role.
Lemma 7 Let
be a nonempty closed convex subset of a Banach space
and
satisfies condition (
) with
. Let
be a sequence generated by (8), then
exists for each
.
Let
. By Proposition (5) part 2), we have
which implies that
Using the values of
and
, we have
Thus, the sequence
is bounded. Also,
is non increasing. Consequently,
exists for each
. The following Theorem is useful for the next results.
Theorem 8 Let
is a uniformly convex Banach space and
is a nonempty convex subset of
. Also, the mapping
satisfies Condition
. Let
be a sequence which is formulated by (8). Then, the set of all fixed points i.e.
iff
is bounded and limiting value of
is 0 for
.
Let,
and
. Consequently, by Lemma (7), there is an existence of
which proves that the sequence
is bounded. Let
(10)
Following the proof of Lemma (3),
(11)
By the proof of Lemma (7). It follows that
and hence we have
Hence, we have
(12)
using the Equations (10) and (12)
(13)
From Equation (13)
Hence,
(14)
Now, using (10) and (12) with (14) with Lemma (6)
(15)
Conversely, let
. By Proposition (5) 3), for
,
By Proposition (5)
Since,
we have
which confirms that
. Since,
is uniformly convex Banach space. Hence,
.
Now, we prove our weak convergence result.
Theorem 9 Let
be a uniformly Banach space with Opial’s property.
is closed and convex subset of
and
satisfying Condition
with
. Then, the sequence
formulated by (8) is a convergent sequence, which converges weakly to
, where
.
Using aforementioned Theorem (8), the sequence
is bounded and we have null sequence as
. It is given that,
is uniformly convex. Consequently,
is reflexive. So, there is an existence of the subsequence
of
in such a manner that
is convergent and converges weakly to some
. By Proposition (5) part (v), we have
. It is sufficient to show that
converges weakly to
. In fact, if
does not converges weakly to
. Then,
a subsequence
of
and
such that
is convergent sequence and converges weakly to
and
. By Theorem (4),
. Considering Opial’s property together with Lemma (7), we have
It really is an ambiguity. So,
. Thus,
is convergent and converges weakly to
.
Theorem 10 Let
, where
be a uniformly Banach space and
be a mapping satisfying
. Then,
generated by (8) converges to an element of
iff
or
.
The necessity is self-evident. Assume, however, that
and
, from Lemma (7),
exists for each
. Hence,
, by based on the assumption. We prove that
is a sequence which is Cauchy in
. It is given that
, for a given
, thereis an existence of
sch that for each
,
implies,
(16)
In particular,
. It confirms the existence of
such that
It proves that the sequence
is Cauchy in
. Also,
is a closed subset of a Banach space
. Consequently, there is an existence of a point
in such a manner that
Now,
gives that
. As we know that
is closed, hence from Lemma (3),
.
We now prove the following Theorem using Condition (C).
Theorem 11 Let
, where
be a uniformly Banach space and
be a mapping satisfying
. Then,
generated by (8) converges strongly to an element of
provided that
satisfies Condition (C).
By using the Theorem (8), we have
Thus, by Condition (C), we obtain
Now that all of Theorem (11)’s have been met,
converges strongly to a fixed point of
as a consequence of its conclusion.
5. Conclusion
Our work deals with AK' iteration scheme to approximate fixed point for Suzuki generalized nonexpansive mapping which satisfy
condition in the framework of Banach spaces. With the help of examples, it is proved that AK' iteration scheme is more efficient than
and S iteration schemes. AK' iteration scheme can be used to find the solution of functional Volterra-Fredholm integral equation and absolute value equations.
Acknowledgements
Sincere thanks to anonymous reviewers for commenting on earlier versions of this paper, and special thanks to managing editor Hellen XU for a rare attitude of high quality.