Research Article
General Higher-Order Lipschitz Mappings
Joseph Frank Gordon
Department of Mathematics, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
Correspondence should be addressed to Joseph Frank Gordon; jgordon@aims.edu.gh
Received 20 January 2021; Revised 12 March 2021; Accepted 19 March 2021; Published 1 April 2021
Academic Editor: Ching-Feng Wen
Copyright © 2021 Joseph Frank Gordon. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
In this paper, we introduce a new class of mappings and investigate their fixed point property. In the first direction, we prove a
fixed point theorem for general higher-order contraction mappings in a given metric space and finally prove an approximate fixed
point property for general higher-order nonexpansive mappings in a Banach space.
1. Introduction
Given a complete metric space (X,d), the most well-studied
types of self-maps are referred to as Lipschitz mappings (or
Lipschitz maps, for short), which are given by the metric
inequality:
d(Tx, Ty) ≤ α d(x, y), (1)
for all x, y ∈ X, where α ≥ 0 is a real number, usually re-
ferred to as the Lipschitz constant of T. Now, for technical
and historical reasons, we classify Lipschitz mappings into
three categories, thus contraction mappings for the case
where 0 ≤ α < 1, nonexpansive mappings for the case where
α � 1, and expansive mappings for the case where α > 1.
In 2007, Goebel and Japon Pineda [1] introduced the
so-called mean nonexpansive mappings which are class of
mappings more general than the class of nonexpansive
mappings. us, given a Banach space (X, ‖ · ‖) and a
nonempty subset C of X, a mapping T: C ⟶ C is called
mean nonexpansive (or α-nonexpansive) if, for some α �
(α
1
, α
2
, ... , α
n
) with
n
k�1
α
k
� 1, α
k
≥ 0 for all k, and
α
1
, α
n
> 0, we have
n
k�1
α
k
T
k
x − T
k
y
�
�
�
�
�
�
�
�
�
�
≤ ‖x − y‖, forall x, y ∈ C. (2)
It is obvious that all nonexpansive mappings are mean
nonexpansive mappings but the converse may not be true (see
for instance [2], examples 2.3 and 2.4). Goebel and Jap´ on
Pineda further suggested the class of (α,p)-nonexpansive
maps. A self-map T: C ⟶ C is called (α,p)-nonexpansive
if, for some α �(α
1
, α
2
, ... , α
n
) with
n
k�1
α
k
� 1, α
k
≥ 0 for
all k, and α
1
, α
n
> 0 and for some p ∈ [1, ∞),
n
k�1
α
k
T
k
x − T
k
y
�
�
�
�
�
�
�
�
�
�
p
≤ ‖x − y‖
p
, (3)
for all x, y ∈ C. It is easy to check that (α,p)-nonexpansive
map for p > 1 is also α-nonexpansive, but the converse does
not hold (see [3] for details), whereas nonexpansive map-
pings are uniformly continuous and that continuous, mean
nonexpansive mappings may not generally be continuous as
seen in the following example taken from [2], example 2.2.
Example 1. Let f: [0, 1] ⟶ [0, 1] be given by
f(x) ≔
1, x � 0,
0, x ≠ 0.
(4)
Clearly, f is discontinuous but a mean nonexpansive
mapping.
In 2015, Ezearn [4] introduced a new class of mappings
called higher-order Lipschitz mappings which are seen as a
generalization of inequality (1). us, a mapping
Hindawi
Journal of Mathematics
Volume 2021, Article ID 5570373, 7 pages
https://doi.org/10.1155/2021/5570373