R E S E A R C H
Open Access
Nonlocal boundary value problems for
second-order nonlinear Hahn
integro-difference equations with integral
boundary conditions
Umaphon Sriphanomwan
1, Jessada Tariboon
1,4*, Nichaphat Patanarapeelert
1, Sotiris K Ntouyas
2,3and
Thanin Sitthiwirattham
5*Correspondence:
1Nonlinear Dynamic Analysis
Research Center, Department of Mathematics, Faculty of Applied Science, King Mongkut’s University of Technology North Bangkok, Bangkok, 10800, Thailand
4Centre of Excellence in
Mathematics, CHE, Sri Ayutthaya Rd., Bangkok, 10400, Thailand Full list of author information is available at the end of the article
Abstract
In this paper, we study a boundary value problem for second-order nonlinear Hahn integro-difference equations with nonlocal integral boundary conditions. Our problem contains two Hahn difference operators and a Hahn integral. The existence and uniqueness of solutions is obtained by using the Banach fixed point theorem, and the existence of at least one solution is established by using the Leray-Schauder nonlinear alternative and Krasnoselskii’s fixed point theorem. Illustrative examples are also presented to show the applicability of our results.
MSC: 39A10; 39A13; 39A70
Keywords: Hahn difference equations; boundary value problems; existence; uniqueness; fixed point theorems
1 Introduction
A quantum calculus substitute the classical derivative by a difference operator, which al-lows one to deal with sets of non-differentiable functions. There are many different types of quantum difference operators such ash-calculus,q-calculus, Hahn’s calculus, forward quantum calculus and backward quantum calculus. These operators are also found in many applications of mathematical areas such as orthogonal polynomials, basic hyper-geometric functions, combinatorics, the calculus of variations and the theory of relativity. Some recent results in quantum calculus can be found in [–] and the references cited therein.
Hahn [] introduced his difference operatorDq,ω(see Definition .) whereq∈(, ) and ω> are fixed, which unifies (in the limit) the two best-known and most-used quantum
difference operators: the Jacksonq-difference derivativeDq, whereq∈(, ) (cf.[–]);
and the forward differenceDωwhereω> (cf.[, , ]). The Hahn difference operator
is a successful tool for constructing families of orthogonal polynomials and investigating some approximation problems (cf.[–]).
The right inverse of the Hahn difference operator was introduced by Aldwoah [, ] who defined the right inverse ofDq,ωin the terms of both the Jacksonq-integral containing
the right inverse ofDqand the Nörlund sum involving the right inverse ofω.
Malinowska and Torres [, ] introduced the Hahn quantum variational calculus, while Malinowska and Martins [] studied the generalized transversality conditions for the Hahn quantum variational calculus. Hamzaet al.[, ] studied the theory of lin-ear Hahn difference equations, and investigated the existence and uniqueness results of the initial value problems with Hahn difference equations using the method of successive approximations.
Recently, Sitthiwirattham [] initiated the study of boundary value problems for Hahn difference equations by considering the boundary value problem consisting of the nonlin-ear Hahn difference equation supplemented with nonlocal three-point boundary condi-tions of the form:
Dq,ωx(t) +f
t,x(t),Dp,θx(pt+θ)
= , t∈[ω,T]q,ω,
x(ω) =ϕ(x),
x(T) =λx(η), η∈(ω,T)q,ω,
(.)
where <q< , <ω<T, ω := –qω , ≤λ< T–η–ωω, p=q
m, m∈N, θ =ω(–p –q), f :
[ω,T]q,ω×R×R→Ris a given function, andϕ:C([ω,T]q,ω,R)→Ris a given
func-tional. He proved existence results for (.) by using the Banach and Krasnoselskii fixed point theorems and also gave some numerical examples.
In this paper, motivated by the above papers, we continue the study of boundary value problems for Hahn difference equations by considering the nonlinear boundary value problem for Hahn integro-difference equations with nonlocal integral boundary condi-tions of the form
Dq,ωx(t) =f
t,x(t),Dp,θx(pt+θ),Ψp,θx(pt+θ)
, t∈[ω,T]q,ω,
x(ω) =x(T),
x(η) =μ T
ω
g(s)x(s)dq,ωs, η∈(ω,T)q,ω,
(.)
where <q< , <ω<T,ω:=–qω ,μ T
ωg(r)dq,ωr= ,μ∈R,p=q
m,m∈N,θ=ω(–p –q),
f ∈C([ω,T]q,ω×R×R×R,R), andg∈C([ω,T]q,ω,R+) are given functions, and for ϕ∈C([ω,T]q,ω×[ω,T]q,ω, [,∞))
Ψp,θx(t) := t
ω
ϕ(t,ps+θ)x(ps+θ)dp,θs. (.)
Existence and uniqueness results are proved by using fixed point theorems. Also many special cases and examples are presented.
2 Preliminaries
In the following, there are notations, definitions, and lemmas which are used in proving the main results.
Definition .([]) For <q< ,ω> andf defined on an intervalI⊆Rcontaining
ω:=–qω , the Hahn difference off is defined by
Dq,ωf(t) =
f(qt+ω) –f(t)
t(q– ) +ω fort=ω,
and Dq,ωf(ω) =f(ω), provided thatf is differentiable at ω. We callDq,ωf the q,ω
-derivative off, and say thatf isq,ω-differentiable onI.
This operator unifies and generalizes two well-known difference operators. The first is Jacksonq-difference operator defined by
Dq,f(t) = ⎧ ⎨ ⎩
f(t)–f(qt)
t(–q) , t= ,
f(), t= , (.)
provident thatf() exists. Heref is supposed to be defined on aq-geometric setA⊂R, for whichqt∈Awhenevert∈A.
The second operator is the forward difference operator
D,ωf(t) =
f(t+ω) –f(t)
ω , (.)
whereω> is fixed.
Lettinga,b∈I⊆Rwitha<ω<band [k]q=–q
k
–q,k∈N:=N∪ {}, we define theq, ω-interval by
[a,b]q,ω:= qka+ω[k]q:k∈N
∪ qkb+ω[k]q:k∈N
∪ {ω}
= [a,ω]q,ω∪[ω,b]q,ω
= (a,b)q,ω∪ {a,b}= [a,b)q,ω∪ {b}= (a,b]q,ω∪ {a}.
Example . The interval [
, ],can be expressed by
,
,
=
,
,
,
,
, ,
, ,, . . .
∪
, , , ,
,
, . . .
∪ {}.
An essential function which plays an important role in Hahn’s calculus ish(t) =qt+ω. This function is normally taken to be defined on an intervalI, which contains the number
ω=–qω . Note thathis a contraction,h(I)⊆I,h(t) <tfort>ω,h(t) >tfort<ω, and
h(ω) =ω. One can see that thekth-order iteration ofh(t) is given byhk(t) =qkt+ω[k]q,
t∈I. Observe that, for eachs∈[a,b]q,ω, the sequence{qks+ω[k]q}∞k=is uniformly
Iff isq,ω-differentiablentimes onq,ω-intervalIq,ω, we define the higher-order
deriva-tives by
Dnq,ωf(s) :=Dq,ωDn–q,ωf(s),
whereD
q,ωf(s) :=f(s),s∈Iq,ω⊂R.
Next, we introduce the right inverse of the operatorDq,ω, the so-called q, ω-integral
operator.
Definition .([]) LetIbe any closed interval ofRcontaininga,bandω. Assuming
thatf :I→Ris a given function, we define theq,ω-integral off fromatobby
b
a
f(t)dq,ωt:= b
ω
f(t)dq,ωt– a
ω
f(t)dq,ωt,
where
t
ω
f(s)dq,ωs=Iq,ωf(t) =
t( –q) –ω ∞
k=
qkftqk+ω[k]q
, x∈I,
is the convergent series atx=aandx=b.f is calledq,ω-integrable on [a,b] and the sum to the right hand side of the above equation will be called the Jackson-Nörlund sum.
We note that the actual domain of the functionf is [a,b]q,ω⊂I.
The following lemma is thefundamental theorem of Hahn calculus.
Lemma .([]) Let f :I→Rbe continuous atω.Define
F(x) :=
x
ω
f(t)dq,ωt, x∈I,
then F is continuous atω.Furthermore,Dq,ωF(x)exists for every x∈I and
Dq,ωF(x) =f(x).
Conversely,
b
a
Dq,ωF(t)dq,ωt=F(b) –F(a) for all a,b∈I.
Next, we give some auxiliary lemmas for simplifying calculations.
Lemma .([]) Let <q< ,ω> and x:I→Rbe continuous atω.Then t
ω r
ω
x(s)dq,ωs dq,ωr= t
ω t
qs+ω
x(s)dq,ωr dq,ωs.
Remark . Observe that
t
ω t
qs+ω
x(s)dq,ωr dq,ωs= t
ω
Lemma .([]) Let <q< andω> ,then
t
ω
dq,ωs=t–ω and t
ω
t– (qs+ω)dq,ωs=
(t–ω)
+q .
Lemma . Let <q< andω> ,then the following equation holds:
t
ω
· · ·
t
ω
ntimes
dq,ωs· · ·dq,ωr=
(t–ω)n
[n]q!
, (.)
where[n]q! = n
k= –qk
–q.
Proof Mathematical induction will be used in our proof as follows. Forn= , we have
t
ω
dq,ωs=
t( –q) –ω ∞
k=
qk= (t–ω),
which means that equation (.) is true forn= .
Suppose that equation (.) holds forn=k. Hence, forn=k+ , we have
t
ω
· · ·
t
ω k+ times
dq,ωs· · ·dq,ωr= t
ω
(r–ω)k
[k]q!
dq,ωr
=[t( –q) –ω] [k]q!
∞
k=
qktqk+ω[k]q–ω k
=( –q)(t–ω) [k]q!
∞
k=
qktqk–ωqk k
=( –q)(t–ω) [k]q!
∞
k=
qkqk(t–ω)k
=( –q)(t–ω)
k+
[k]q!( –qk+)
=(t–ω)
k+
[k+ ]q!
.
Thus, equation (.) holds forn=k+ . By the principle of induction, equation (.) is true
for alln∈N.
The following lemma deals with the linear variant of problem (.) and gives a presen-tation of the solution.
Lemma . LetμωT
g(r)dq,ωr= and h∈C([ω,T]q,ω,R)be a given function.Then the
function x is a solution of the problem
Dq,ωx(t) =h(t), t∈[ω,T]q,ω, (.)
if and only if
Proof By Lemma . and Remark ., a general solution for (.) can be written as
x(t) =
From the boundary conditions of (.), we obtain
C= –
On the other hand, by taking the second-orderq,ω-derivative to (.), we have (.). It
3 Existence and uniqueness results
In this section, we present the existence and uniqueness of solutions for problem (.). Let
X= x|x∈C[ω,T]q,ω,R
andDp,θx∈C
[ω,T]q,ω,R
be the Banach space of all continuous functionsx: [ω,T]q,ω→Rwith the norm defined
by
xX=x+Dp,θx,
wherex=max{|x(t)|:t∈[ω,T]q,ω}andDp,θx=max{|Dp,θx(pt+θ)|:t∈[ω,T]q,ω}.
We define an operatorF:X→Xby
(Fx)(t)
=
t
ω
t– (qs+ω)fs,x(s),Dp,θx(ps+θ),Ψp,θx(ps+θ)
dq,ωs
–(t–ω) T–ω
T
ω
T– (qs+ω)fs,x(s),Dp,θx(ps+θ),Ψp,θx(ps+θ)
dq,ωs
+
Ω
μ T
ω r
ω
g(r)r– (qs+ω)fs,x(s),Dp,θx(ps+θ),Ψp,θx(ps+θ)
dq,ωs dq,ωr
–
η
ω
η– (qs+ω)fs,x(s),Dp,θx(ps+θ),Ψp,θx(ps+θ)
dq,ωs
+
T–ω T
ω
T– (qs+ω)fs,x(s),Dp,θx(ps+θ),Ψp,θx(ps+θ)
dq,ωs
×
η–ω–μ T
ω
g(r)(r–ω)dq,ωr
, (.)
whereΩ= is defined by (.),p=qm,m∈Nandθ=ω(–p–q).
Obviously, problem (.) has solutions if and only if the operatorFhas fixed points.
3.1 Existence and uniqueness result via Banach’s fixed point theorem
Our first result concerns existence and uniqueness of solutions of problem (.) and is based on Banach’s fixed point theorem.
Theorem . Let
ϕ=max ϕ(t,ps+θ) : (t,ps+θ)∈[ω,T]q,ω×[ω,T]q,ω
. (.)
Assume that:
(H) there exist functionshi∈C([ω,T]q,ω,R+),i= , , such that
f(t,x,x,x) –f(t,y,y,y)≤h(t)|x–y|+h(t)|x–y|+h(t)|x–y|
≤
This implies, by (H), thatFis a contraction. Therefore, by Banach’s fixed point theorem, F has a unique fixed point, which is the unique solution of problem (.) on [ω,T]q,ω.
Corollary . If hi=L,i= , , with L<[+ϕ(T–ω)](Φ+Φ) in Theorem.,then problem
(.)has a unique solution on[ω,T]q,ω.
Example . Consider the following boundary value problem for second-order Hahn integro-difference equation:
⎧ ⎨ ⎩
D
/,/x(t) =f(t,x(t),Dp,θx(pt+θ),Ψp,θx(pt+θ)),
x() =x(), x(,/) = (/)ecos(πs)x(s)d /,/s,
(.)
where
ft,x(t),Dp,θx(pt+θ),Ψp,θx(pt+θ)
=
( +t)( +|x(t)|)
e–sin(πt)x+ |x|+e–cos(πt)|D/,/x|
+e–t|Ψ/,/x|
(.)
and
Ψ/,/x(t) = t
e–((/)s+/–t)
x
(/)s+ /d/,/s.
Hereq= /,ω= /,ω= ,p= /,m= ,θ = /,T= ,η= ,/,μ=
/,g(t) =ecos(πt),ϕ(t,ps+θ) =e–((/)s+/–t)
. By direct computation, we find that
f(t,x,Dp,θx,Ψp,θx) –f(t,y,Dp,θy,Ψp,θy)
≤e–sin
(πt)
+t x–y+
e–cos(πt)
+t Dp,θx–Dp,θy+
e–t
+tΨp,θx–Ψp,θy,
ϕ= /, and (H) is satisfied withh(t) = e –sin(πt)
+t , h(t) = e –cos(πt)
+t ,h(t) = e –t
+t. So, Φ= .. From <g(t) <e, (H) is satisfied withN=e. By the given data we find
Φ= .,Φ= .. Therefore, we can compute that
S=Φ(Φ+Φ) = ..
Hence, by Theorem ., problem (.) with (.) has a unique solution on [, ]/,/.
3.2 Existence result via Leray-Schauder’s nonlinear alternative
Lemma .(Nonlinear alternative for single valued maps []) Let E be a Banach space, C a closed,convex subset of E,U an open subset of C and∈U.Suppose that F:U→C is a continuous,compact(that is,F(U)is a relatively compact subset of C)map.Then either
(i) Fhas a fixed point inU,or
(ii) there is au∈∂U(the boundary ofUinC)andλ∈(, )withu=λF(u).
Theorem . Let f : [ω,T]q,ω×R×R×R→Rbe a continuous function.In addition,
(H) there exist a functionm∈C([ω,T]q,ω,R),and continuous nondecreasing functions
Firstly, we show that the operatorFmaps bounded sets into bounded sets in the spaceX. LetBr={x∈X:xX≤r},r> . For anyx∈Br, putting
and using the inequalities
and
is equicontinuous and uniformly bounded. The Arzelá-Ascoli theorem implies thatFis completely continuous.
The result will follow from the Leray-Schauder nonlinear alternative (Lemma .) once we have proved the boundedness of the set of all solutions to equationsx=λFxforλ∈
In view of (H), there existsMsuch thatxX=M. Let us set
U= x∈C[ω,T]q,ω,R
:xX<M
.
Note that the operatorF:U→C([ω,T]q,ω,R) is continuous and completely
continu-ous. From the choice ofU, there is nox∈∂Usuch thatx=λFxfor someλ∈(, ). Con-sequently, by the nonlinear alternative of Leray-Schauder type (Lemma .), we deduce thatF has a fixed pointx∈Uwhich is a solution of problem (.). This completes the
proof.
Corollary . Suppose that a continuous function f satisfies|f(t,x,y,z)| ≤K(|x|+|y|+|z|), K≥.If K[ +ϕ(T–ω)](Φ+Φ) < ,then problem(.)has at least one solution on
[ω,T]q,ω.
Example . Consider the following boundary value problem for second-order Hahn integro-difference equation:
⎧ ⎨ ⎩
D
/,/x(t) =f(t,x(t),Dp,θx(pt+θ),Ψp,θx(pt+θ)),
x() =x(), x(,/) = (/)ecos(πs)x(s)d /,/s,
(.)
where
ft,x(t),Dp,θx(pt+θ),Ψp,θx(pt+θ)
=
(t+ )
e
–|x|sin|x|+ |D/,/x|
( +|D/,/x|)
+ |Ψ/,/x|
( +|Ψ/,/x|)
+
(.)
and
Ψ/,/x(t) = t
e–((/)s+/–t)
x
(/)s+ /d/,/s.
Hereq= /,ω= /,ω= ,p= /,m= ,θ= /,T= ,η= ,/,μ= /,
g(t) =ecos(πt),ϕ(t,ps+θ) =e–((/)s+/–t)
. Since
f(t,x,Dp,θx,Ψp,θx)
≤
(t+ )
|x|+
|D/,/x|+
|Ψ/,/x|+
,
ϕ = /, (H) is satisfied with m(t) = (t+) , ψ(|x|) = |x|, ψ(|D/,/x|) =
|D/,/x| + , ψ(|Ψ/,/x|) =
|Ψ/,/x| + . In addition, we see that
<g(t) <e, then (H) is satisfied withN=e. From the above information, we find that Φ= ., Φ = .. Therefore, there exists a constant M> .
satisfy-ing (H). Hence, by Theorem ., problem (.) with (.) has at least one solution on
3.3 Existence result via Krasnoselskii’s fixed point theorem
The final existence result is based on Krasnoselskii’s fixed point theorem.
Lemma . (Krasnoselskii’s fixed point theorem []) Let S be a closed, convex and nonempty subset of a Banach space X.Let A,B be the operators such that(a)Ax+By∈S whenever x,y∈S; (b)A is compact and continuous; (c)B is a contraction mapping.Then there exists z∈S such that z=Az+Bz.
Theorem . Assume that(H)and(H)hold.In addition we assume that:
(H) |f(t,x,y,z)| ≤μ(t),for eacht∈[ω,T]q,ω,x,y,z∈Randμ∈C([ω,T],R+).
Then problem(.)has at least one solution on[ω,T]q,ω,provided
T–ω
+q ( +T–ω)Φ< , (.)
whereΦis defined by(.).
Proof Consider the operatorF:X→Xdefined by (.) as
(Fx)(t) = (Fx)(t) + (Fx)(t), t∈[ω,T]q,ω, (.)
where
(Fx)(t) = –(t–ω) T–ω
T
ω
T– (qs+ω)fˆx(s)dq,ωs
and
(Fx)(t)
=
t
ω
t– (qs+ω)fˆx(s)dq,ωs
+
Ω
μ T
ω r
ω
g(r)r– (qs+ω)fˆx(s)dq,ωs dq,ωr– η
ω
η– (qs+ω)fˆx(s)dq,ωs
+
T–ω T
ω
T– (qs+ω)fˆx(s)dq,ωs
η–ω–μ T
ω
g(r)(r–ω)dq,ωr
.
Setting max{μ(t) :t∈[ω,T]q,ω}=μ and choosingρ≥ μ(Φ+Φ) we consider
Bρ={x∈C([ω,T]q,ω,R) :xX≤ρ}. For anyx,y∈Bρwe have (Fx)(t) + (Fy)(t)
≤
t
ω
t– (qs+ω)fˆy(t)dq,ωs+
(t–ω)
T–ω T
ω
T– (qs+ω)fˆx(t)dq,ωs
+
|Ω|
μ T
ω r
ω
g(r)r– (qs+ω)fˆy(t)dq,ωs dq,ωr
–
η
ω
+
It is easy to prove that
Fx–Fy ≤(T–ω) which implies, by (.), thatFis a contraction mapping.
Continuity of f implies that the operator F is continuous. Also, F is uniformly bounded onBρand equicontinuous, as proved in Theorem .. SoFis relatively compact
onBρ. Hence, by the Arzelá-Ascoli theorem,Fis compact onBρ. Thus all the
assump-tions of Lemma . are satisfied. So the conclusion of Lemma . implies that problem
Corollary . Suppose that a continuous function f satisfies(H)with hi=L,i= , , ,
and|f(t,x,y,z)| ≤K,K> .IfT–ω
+q ( +T–ω)( +ϕ(T–ω))L< then problem(.)has
at least one solution on[ω,T]q,ω.
Example . Consider the boundary value problem for second-order Hahn
integro-difference equation in Example . with
ft,x(t),Dp,θx(pt+θ),Ψp,θx(pt+θ)
=
( +t)( +|x(t)|)
e–sin(πt)x+ |x|+e–cos(πt)|D/,/x|
+e–t|Ψ/,/x|
. (.)
Now, we see that
f(t,x,Dp,θx,Ψp,θx) –f(t,y,Dp,θy,Ψp,θy)
≤e–sin
(πt)
+t x–y+
e–cos(πt)
+t Dp,θx–Dp,θy+
e–t
+tΨp,θx–Ψp,θy.
Then (H) is satisfied withh(t) =e –sin(πt)
+t ,h(t) =e –cos(πt)
+t ,h(t) = e –t
+t. Therefore, we
can find thatΦ= ., and
S=Φ(Φ+Φ) = . > .
Thus, Theorem . cannot be applied in this case. However, (H) is satisfied withμ(t) =
+t, by|f(t,x,Dp,θx,Ψp,θx)| ≤+t . Indeed, we find that
T–ω
( +q)( +T–ω)Φ= . < .
Then, by using Theorem ., problem (.) with (.) has at least one solution on [/, ]/,/.
Acknowledgements
This research is partially supported by the Centre of Excellence in Mathematics, the Commission on Higher Education, Thailand.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
All authors contributed equally in this article. They read and approved the final manuscript.
Author details
1Nonlinear Dynamic Analysis Research Center, Department of Mathematics, Faculty of Applied Science, King Mongkut’s
University of Technology North Bangkok, Bangkok, 10800, Thailand.2Department of Mathematics, University of Ioannina,
Ioannina, 451 10, Greece.3Nonlinear Analysis and Applied Mathematics (NAAM)-Research Group, Department of
Mathematices, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah, 21589, Saudi Arabia. 4Centre of
Excellence in Mathematics, CHE, Sri Ayutthaya Rd., Bangkok, 10400, Thailand.5Mathematics Department, Faculty of
Science and Technology, Suan Dusit University, Bangkok, 10300, Thailand.
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