Palestine Journal of Mathematics
Vol. 8(2)(2019) , 182–190 © Palestine Polytechnic University-PPU 2019
HYBRID ITERATION METHOD FOR FIXED POINTS OF
ASYMPTOTICALLY φ−DEMICONTRACTIVE MAPS IN
REAL HILBERT SPACES
Uko Sunday Jim
Communicated by Ayman Badawi
MSC 2010 Classifications: Primary 47H09, 47H10; Secondary 47J05, 65J15.
Keywords and phrases: Hybrid iteration method, Asymptotically φ-demi- contractive, Fixed point, Uniformly Lips-
chitzian, Hilbert spaces.
We acknowledge the anonymous reviewers for their useful comments.
Abstract. A strong convergence theorem of Hybrid iteration method to fixed points of
asymptotically φ−demicontractive mapping is proved in real Hilbert spaces. Our results extend,
generalize and complement the results of Wang [8], Osilike, Isiogugu and Nwokoro [14], and
extend several others from asymptotically demicontractive to the more general class of asymp-
totically φ−demicontractive maps (see for example [2, 11, 17]).
1 Introduction
Let K be a nonempty subset of a real Hilbert space H. A mapping T : K −→ K is said to be
asymptotically φ−demicontractive with a sequence {k
n
}
∞
n=1
⊆ [1, ∞), lim
n→∞
k
n
= 1,(see for
example, [3, 4]), if F (T )= {x ∈ K : Tx = x} = ∅ and there exists an increasing continuous
function φ : [0, ∞) → [0, ∞) with φ(0)= 0 such that
‖T
n
x − p‖
2
≤ k
n
‖x − p‖
2
+ ‖x − T
n
x‖
2
− φ(‖x − T
n
x‖), (1.1)
∀x ∈ K, p ∈ F (T ) and n ≥ 1.
A mapping T : K −→ K is said to be asymptotically demicontractive with a sequence
{a
n
}
∞
n=1
⊆ [1, ∞), lim
n→∞
a
n
= 1, if F (T ) = ∅ and ∀x ∈ K, p ∈ F (T ), ∃ a k ∈ [0, 1) ∋
‖T
n
x − p‖
2
≤ a
2
n
‖x − p‖
2
+ k‖(I − T
n
)x‖
2
, (1.2)
A mapping T : K −→ K is said to be k−strictly asymptotically pseudocontractive with a
sequence {k
n
}
∞
n=1
⊆ [1, ∞),
lim
n→∞
k
n
= 1 if ∀x, y ∈ K, n ∈ N, ∃ a k ∈ [0, 1) ∋
‖T
n
x − T
n
y‖
2
≤ k
n
‖x − y‖
2
+ k‖(I − T
n
)x − (I − T
n
)y‖
2
, (1.3)
where I is the identity operator. The class of k−strictly asymptotically pseudocontractive and
asymptotically demicontractive maps were first introduced in Hilbert spaces by Qihou [10]. Ob-
serve that a k−strictly asymptotically pseudocontractive map with a nonempty fixed point set
F (T ) is asymptotically demicontractive. An example of a k−strictly asymptotically pseudocon-
tractive map is given in Osilike et al. [16].
Furthermore, T is uniformly L−Lipschitzian if there exists a constant L> 0 ∋
‖T
n
x − T
n
y‖≤ L‖x − y‖, (1.4)
∀x, y ∈ K and n ≥ 1.
The class of asymptotically φ−demicontractive maps was first introduced in arbitrary real Ba-
nach spaces by Osilike and Isiogugu [13]. It is shown in [13] that the class of asymptotically
demicontractive map is a proper subclass of the class of asymptotically φ−demicontractive