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1. International Journal of Mathematics and Statistics Invention (IJMSI)
E-ISSN: 2321 – 4767 P-ISSN: 2321 - 4759
www.ijmsi.org Volume 2 Issue 4 || April. 2014 || PP-58-66
www.ijmsi.org 58 | P a g e
Controllability of Neutral Integrodifferential Equations with
Infinite Delay
Jackreece P. C.
Department of Mathematics and Statistics, University of Port Harcourt, Port Harcourt, Nigeria.
ABSTRACT: In this paper sufficient conditions for the controllability of nonlinear neutral integrodifferential
equations with infinite delay where established using the fixed point theorem due to Schaefer.
KEYWORDS: Controllability, Infinite delay, Neutral Integrodifferential equation, Schaefer fixed point.
I. INTRODUCTION
In this paper, we establish a controllability result to the following nonlinear neutral integrodifferential
equations with infinite delay:
1.1
0,,,,,
0
x
txtfdsxstgtButxtAxthtx
dt
d
t
t
st
where the state .x takes values in the Banach space X endowed with the norm . , the control function .u
is given in the Banach space of admissible control function UJL ,2
with U as a Banach space.
XADtA : is an infinitesimal generator of a strongly continuous semigroup of bounded linear operator
0, ttT in X . is a bounded linear operator from U into X , where XJJg : ,
XJf : , and XJh : are given functions. The delay Xxt 0,: defined by
txxt belongs to some abstract phase space , which will be a linear space of functions mapping
0, into X endowed with the seminorm
. in . Controllability problems of linear and nonlinear
systems represented by Ordinary differential Equations in finite dimensional space has been studies extensively
[6, 15]. Several authors extended the controllability concept to infinite dimensional systems in abstract spaces
with unbounded operators [1, 2, 8]. There are many systems that can be written as abstract neutral functional
equations with infinite delays. In recent years, the theory of neutral functional differential equations with infinite
delay in infinite dimension has received much attention [4, 7, 10]. Meanwhile, the controllability problem of
such systems was also discussed by several scholars. Meili et al. [13] studied the controllability of neutral
functional integrodifferential systems in abstract spaces using fractional power of operators and Sadovski fixed
point theorem. Balachandran and Nandha [5] established sufficient conditions for the controllability of neutral
functional integrodifferential systems with infinite delay in Banach spaces by means of Schaefer fixed point
theorem. Li et al. [12] used Hausdoff measure of noncompactness and Kakutani’s fixed point theorem to
establish sufficient conditions for the controllability of nonlinear integrodifferential systems with nonlocal
condition in separable Banach space. The purpose of this paper is to establish a set of sufficient conditions for
the controllability of neutral integrodifferential equations with infinite delay using Schaefer fixed point theorem.
II. PRELIMINARIES
In this section, we introduce notations, definitions and theorems which are used throughout this paper.
In the study of equations with infinite delay such as Eq. (1.1), we need to introduce the phase space. In this
paper we employ an axiomatic definition of the phase space first introduced by Hale and Kato [9] and widely
discussed by Hino et al [11]. The phase space is a linear space of functions mapping ]0,( into
X endowed with the seminorm
. and assume that satisfies the following axioms:
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(A1) If ,0,,: bXbx is continuous on b,0 and 0x , then for every bt ,0 the
Following conditions hold:
(i) tx is in
(ii)
txHtx
(iii)
00:sup xtMtssxtKxt
where 0H is a constant; ),0[),0[:, MK , K is continuous and M is locally bounded, and
MKH ,, are independent of .x .
(A2) For the function .x in (A1), tx is a -valued continuous function on ],0[ b .
(A3) The space is complete.
We need the fixed point theorem as stated below,
Schafer’s theorem [14]: Let S be a convex subset of a normed linear space E and S0 . Let SSF : be
completely continuous operator and let
1,0: someforxFxSxF
Then either F is unbounded or F has a fixed point.
We assume the following hypothesis:
(H1) A is the infinitesimal generator of a compact semigroup of bounded linear operators 0, ttT on
X and their exists 1M and 01 M such that
MtT and 1MtAT .
(H2) For XJh : is completely continuous and there exists constants 21,cc such that 1
~
1 cK
and
21, ccth
,,0 bt , where JttKK :max
~
.
(H3) The function XJf : satisfies the following conditions
(i). For each Jt , the function XJf : is continuous.
(ii) For each , the function XJf :,; is strongly measurable.
(iii). For each positive integer k, there exists bLk ,0. 1
such that
eaJttkxxtf kt .,:,sup .
and
xJtxxtf ,,,
where ,0[),0[: is a continuous nondecreasing function.
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(H4) XJJg : is continuous and there exists 0N , such that
Nstg ,,
For every .0 bts
(H5) for each ,
0
,,lim)(
a
a dssstgtq exists and it is continuous. Further there exists
01 N such that .1Ntq
(H6) there exists a compact set XV , such that ,,,,, sgtTsButTsftT and
VsqtT for all , , and .0 bts
(H7) The linear operator XUJLW ,: 2
, defined by
b
dssBusbTWu
0
has an inverse operator
1
W , which takes values in WUJL ker/,2
and there exist positive constants
0, 43 MM such that 4
1
3 MWandMB
(H8)
b
s ss
ds
dssm
0
~
where
dsxMMNbbMN
dscxcMcxcccMxMMN
b
s
b
st
0
1
0
21121211433 0
MNbMNMNbcMcccMKM
cK
c
1321121
1
0
~~
~
1
1
JttMM :max
~
11
11
~
1
~
,~
1
~
max~
cK
MK
cK
cMK
tm
Definition 2.1: The system (1.1) is said to be controllable on the interval J iff, for every Xxx b ,0 , there
exists a control UJLu ,2
such that the mild solution tx of (1.1) satisfies 00 xx and bxbx .
Definition 2.2: A function Xbx ,: is called a mild solution of the integrodifferential equation (1.1)
on [0, b] iff ,
1.2,0,,,
,,,00
0 0
0
btdsxsfdxsgsqsBustT
dsxshstATxthhtTtx
t
s
t
s
t
tt
is satisfied. See [3,10]
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III. MAIN RESULT
Theorem 3.1: Assume that (H1)-(H8) holds. Then the system (1.1) is controllable.
Proof: Consider the map defined by
)1.3(,,,
,,,00
0 0
0
t
s
t
s
t
st
JtdsxsfdxsgsqsBustT
dsxshstATxthhttx
and define the control function tu as
)2.3(,,,
,,,00
0 0 0 0
0
1
b b s b
s
b
sbb
tdsxsfsbTdsdxsgsbTdssqsbT
dsxshsbATxbhhbTxWtu
First we show that there is a priori bound 0K such that JtKxt , , where K depends only on b and
on the function . . Then we show that the operator has a fixed point, which is then a solution to the system
(1.1). Obviously, 1xbx , which means that the control u steers the system from the initial function
to 1x in time b, provided that the nonlinear operator has a fixed point.
Substituting (3.2) into (2.1) we obtain
t
st dsxshstATxthhtTtx
0
,,,00
t b
sb dsxshsbATxbhhbTxBWtT
0 0
1
1
,,,00
b b s b
s ddsxsfsbTdsdxsgsbTdssqsbT
0 0 0 0
,,,
t
s
s
dsxsfdxsgsqstT
0 0
,,,
Then, we have
MNbMNMNdscxcMcxcccMtx
t
st 13
0
21121210
dsxM
t
s
0
From which using Axiom (A1)(iii), it follows that
tMtssxtKxt 0:sup
MtssxK
~
0:sup
~
MNbMNMNbcMcccMKM 13212210
~~
t t
sss dsxMKdsxcMKxcK
0 0
111
~~
sup
~
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Let tsxt s 0:sup , then the function t is continuous and nondecreasing and from Axiom
(A2) we have
MNbMNMNbcMcccMKMt 13211210
~~
tt
dsMKdsscMKtcK
00
111
~~~
From which it follows that
t t
dss
Kc
MK
dss
cK
cMK
ct
0 0
11
11
1
~
~
1
~
Denoting the right hand side of the above inequality as t , we have c0 , Jttt , and
s
cK
MK
s
cK
cMK
t
11
11
~
1
~
~
1
~
s
cK
MK
s
cK
cMK
11
11
~
1
~
~
1
~
sstm
which implies that
Jt
ss
ds
dssm
ss
dst t
0 0 0
~
This inequality implies that there is a constant K such that JtKt , and hence,
KtKttxt , , where K only depends on b and on the function . .
We now rewrite the initial value problem (1.1) as follows:
For , define ˆ by
atifhtT
tiftht
t
0,00
0,ˆ
If atttytxandy ,,ˆ , then it is easy to see that x satisfies (2.1) if and only if
y satisfies,
0,00 tyty
b
ssbb
t
t
sstt
dsyshsbATybhhbTxBWtT
dsyshstATythhtTty
00
1
1
0
ˆ,ˆ,,00
ˆ,ˆ,,0
Jts
cM
M
scMK
cK
11
11
1
~
~
1
1
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ddsysfsbTdsdysgsbTdssqsbT
b s b
ss
b
0 0 00
ˆ,ˆ,,
JtdsysfdysgsqstT
t s
ss
,ˆ,ˆ,,
0 0
We define the operator 0:,: 0000 yy by
dsyshsbATybhhbTxBWtT
dsyshstATythhtTty
t b
ssbb
t
sstt
0 0
1
1
0
ˆ,ˆ,,00
ˆ,ˆ,,0
ddsysfsbTdsdysgsbTdssqsbT
b b b
ss
0 0 0 0
ˆ,ˆ,,
t s
ss JtdsysfdysgsqstT
0 0
,ˆ,ˆ,,
From the definition of an operator defined on equation (3.1), it can be noted that the equation (2.1) can be
written as
3.310, tyty
Now, we prove that is completely continuous. For any kBy , let btt 210 , then
21 tyty
2211
ˆ,ˆ,,0 2121 tttt ythythhtTtT
2
1
1
ˆ,ˆ, 2
0
21
t
t
ss
t
ss dsyshstATdsyshstTstTA
1
0
1
1
21
ˆ,,00
t
bbybhhbTxBWtTtT
dssqsbTyshsbAT
b b
ss
0 0
ˆ,
ddsysfsbTdsdysgsbT
b b
ss
0 0 0
ˆ,ˆ,,
2
1
ˆ,,001
1
2
t
t
bbybhhbTxBWtT
b b
ss dssqsbTdsyshsbAT
0 0
ˆ,
ddsysfsbTdsdysgsbT
b
ss
b
00 0
ˆ,ˆ,,
1
0 0
21
ˆ,ˆ,,
t s
ss dsysfdysgsqstTstT
2
1 0
2
ˆ,ˆ,,
t
t
s
ss dsysfdysgsqstT
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2211
ˆ,ˆ,,0 2121 tttt ythythhtTtT
1 2
10
2122121
ˆˆt t
t
ssss dscycstATdscycstTstTA (3.4)
1
0
12114321
ˆ,00
t
bb bMNcychMxMMstTstT
b b t
t
ss hMxMMstTdsdsyMdsNM
0 0
1432
2
1
,00ˆ
b b b
bbbb dsdssMdsNdMbMNdscycMcyc
0 0 0 0
121121
ˆˆ
1 2
10
12121
t t
t
dssNNstTdssNNstTstT
The right-hand side of equation (3.4) is independent of ky and tends to zero as 012 tt , since g is
completely continuous and the compactness of tT for 0t implies the continuity in the uniform operator
topology. Thus maps k into an equicontinuous family of functions.
t
sstt dsyshstATythhtTty
0
ˆ,ˆ,,0
t
bbybhhbTxBWstT
0
1
1 ˆ,,00
b b b
ssbs dsysfsbTdssqsbTdsyshsbAT
0 0 0
ˆ,ˆ,
b t s
ss
s
dsdysgysfsqstTdsdsdysgsbT
0 0 00
ˆ,,ˆ,ˆ,,
t
sstt yshtATTythhtT
0
ˆ,ˆ,,0
t
bbybhhbTxBWstTT
0
1
1 ˆ,,00
b b
ss
b
bb dsysfsbTdssqsbTdsyshsbAT
0 00
ˆ,ˆ,
b s
dsdsdysgsbT
0 0
ˆ,,
dsdysgysfsqstTT
t s
ss
0 0
ˆ,,ˆ,
Since tT is a compact operator, the set kytytY : is precompact in X for every ,
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t 0 . Moreover, for every ky we have
t
t
sstttt dsyshstATythythtyty
ˆ,ˆ,ˆ,
t
t
bbybhhMxMMstT
ˆ,,00143
b
ss
b b
ss dsysfstTdssqstTdsyshstAT
00 0
ˆ,ˆ,
dsdsysgysfsqstT
dsdsdysgstT
t
t
s
ss
b s
0
0 0
ˆ,,ˆ,
ˆ,,
Clearly 0 tyty as
0 . Therefore, there is a family of precompact sets which are
arbitrarily close to the set kyty : . Hence, the set kyty : is precompact in X .
Next we prove that the set
00
: bb is continuous. Let 0
1 bnny with yyn in
0
b . We have
t
sssntttnn dsyshyshstATythythtyty st 0
ˆ,ˆ,ˆ,ˆ,
t t
sssn dsyshyshMMMstT s0 0
143
ˆ,ˆ.
b s b
sssnn dsdsysfysfMdsysgysgM s0 0 0
ˆ,ˆ,ˆ,,ˆ,,
t s
nsssn dsysgysgysfysfstT s0 0
ˆ,,ˆ,,ˆ,ˆ,
From the assumption (H1) and the Lebesgue Dominated Convergence theorem we conclude that yyn as
n in
0
b . Thus . is continuous, which completes the proof that . is completely continuous.
Hence there exists a unique fixed point tx for bon . Obviously .x is a mild solution of the system
(1.1) satisfying 1xbx .
IV. CONCLUTION
Sufficient condition for the controllability of the nonlinear neutral integrodiffential equation was established
using Schaefer’s fixed point theorem. First we show that there is a priori bound 0K such
that JtKxt , . Then we show that the operator has a fixed point, which is then a solution to the system
(1.1). Obviously, 1xbx , which means that the control u steers the system from the initial function
to 1x in time b, provided that the nonlinear operator has a fixed point.
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