Nonlinear Analysis 74 (2011) 4293–4299
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Nonlinear Analysis
journal homepage: www.elsevier.com/locate/na
Solution of nonlinear integral equations of Hammerstein type
C.E. Chidume
a,∗
, E.U. Ofoedu
b
a
The Abdus Salam International Centre for Theoretical Physics, Trieste, Italy
b
Department of Mathematics, Nnamdi Azikiwe University, P.M.B. 5025, Awka, Anambra State, Nigeria
article info
Article history:
Received 29 April 2009
Accepted 10 February 2011
MSC:
47H06
47H09
47J05
47J25
Keywords:
Accretive operators
Generalized duality maps
Equations of Hammerstein type
Modulus of smoothness
Uniformly Gâteaux differentiable norm
abstract
Let E be a 2-uniformly real Banach space and F , K : E → E be nonlinear-bounded accretive
operators. Assume that the Hammerstein equation u + KFu = 0 has a solution. A new
explicit iteration sequence is introduced and strong convergence of the sequence to a
solution of the Hammerstein equation is proved. The operators F and K are not required
to satisfy the so-called range condition. No invertibility assumption is imposed on the
operator K and F is not restricted to be an angle-bounded (necessarily linear) operator.
© 2011 Elsevier Ltd. All rights reserved.
1. Introduction
Let E be a real normed space and let S := {x ∈ E :‖x‖= 1}. E is said to have a Gâteaux differentiable norm if the limit
lim
t →0
+
‖x + ty‖−‖x‖
t
exists for each x, y ∈ S . When this limit exists, we say that E is smooth. E is said to have a uniformly Gâteaux differentiable
norm if for each y ∈ S the limit is attained uniformly for x ∈ S . Furthermore, E is said to be uniformly smooth if the limit
exists uniformly for (x, y) ∈ S × S .
Let E be a normed linear space with dimension greater than or equal to 2. The modulus of smoothness of E is the function
ρ
E
:[0, ∞) →[0, ∞) defined by
ρ
E
(t ) := sup
‖x + y‖+‖x − y‖
2
− 1 :‖x‖= 1, ‖y‖= t
.
In terms of the modulus of smoothness, the space E is called uniformly smooth if and only if lim
t →0
+
ρ
E
(t )
t
= 0. E is called
q-uniformly smooth if there exists a constant c > 0 such that ρ
E
(t ) ≤ ct
q
, t > 0. L
p
(and ℓ
p
) spaces, 1 < p < +∞ are
q-uniformly smooth. In particular, L
p
is 2-uniformly smooth if 2 ≤ p < +∞ and p-uniformly smooth if 1 < p < 2. It is easy
∗
Corresponding author. Fax: +39 040224163.
E-mail addresses: chidume@ictp.trieste.it (C.E. Chidume), euofoedu@yahoo.com (E.U. Ofoedu).
0362-546X/$ – see front matter © 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.na.2011.02.017