integral equation (differential) Lipschitz and the type of Picard iterations.
Exercise
was repeated under the same theoreme1
in the message of 28/11/2006
Let (E, II) a real Banach space. <= kIx-yI sur ExE.
C denotes the space of continuous functions
defined on [0, T] with values in E.
space C is equipped with the standard
u, denoted II.II
Let K be a continuous mapping of [0, T] x [0, T) xE
in E satisfies the Lipschitz condition: There
L> 0: IK (t, s, x)-K (t, s, y) I
for all (t, s) [0, T] x [0, T] and x , y
on C (see the proof of theoreme1) by:
S (x) (t) = f (t) + \\ int_ {0} ^ {t} K (t, s, x (s)) ds;
. where f is a fixed element x in C and C
i) Verify that C is stable in S.
ii) for x, y in C, show that
II (S ^ {n} x) - (S ^ {n} y) II
ii) Deduce that S admits a unique fixed point z C.
iii) Show that for each x in C, we have:
IIS ^ {n} x-ZII or
R_ {n) is a constant to be determined.
<= LIx-yI
iv) Search the benefits of this approach.
(Compare with theoreme1)
Proof
i) obvious
ii) Demonstration by recurrence:
for n = 1, the result is évident.Supposons
true has order n, then:
I (S ^ {n +1} x) (t) - (S ^ { n +1} y) (t) I
<= [(LT)^{n}/n!] IIx-yII
= (Lt) ^ {n +1} / (n +1)! IIx-YII <=R_{n}ISx-zI
Taking the sup over [0, T], we obtain
IIS ^ {n +1} xS ^ {n +1} YII
ii) Taking into account the previous inequality (* ) apply
Assertion i) or the assertion ii) the exercise of the message
20/10/2007.
iii) For any x in C, we have:
IIS ^ {n} x-ZII
or R_ {n} = Sigma (i = 0 to infinity) [(LT) ^ {n + i } / (n + i)]
<=\int_{0}^{t} IK(t,s,(S^{n}x)(s))-K(t,s,(S^{n}y)(s))I ds
is the rest of the series expansion of exp (LT).
<= L\int_{0}^{t} I(Sx)(s)-(Sy)(s)Ids
iv) leaves the reader.
<= \int(L^{n+1} s^{n})/n!)Ix(s)-y(s)I ds
(
<= (LT)^{n+1}/(n+1)! IIx-yII (*)
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