Mixing “In the sense of Ibragimov.” Estimate for the rate of approach of a family of integral functionals of a solution of a differential equation with periodic coefficients to a family of wiener processes. Some applications. I
We prove that a bounded 1-periodic function of a solution of a time-homogeneous diffusion equation with 1-periodic coefficients forms a process that satisfies the condition of uniform strong mixing. We obtain an estimate for the rate of approach of a certain normalized integral functional of a solut...
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| Sprache: | Russisch Englisch |
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Institute of Mathematics, NAS of Ukraine
2010
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Ukrains’kyi Matematychnyi Zhurnal| _version_ | 1860508900334239744 |
|---|---|
| author | Bondarev, B. V. Kozyr', S. M. Бондарев, Б. В. Козырь, С. М. Бондарев, Б. В. Козырь, С. М. |
| author_facet | Bondarev, B. V. Kozyr', S. M. Бондарев, Б. В. Козырь, С. М. Бондарев, Б. В. Козырь, С. М. |
| author_sort | Bondarev, B. V. |
| baseUrl_str | https://umj.imath.kiev.ua/index.php/umj/oai |
| collection | OJS |
| datestamp_date | 2020-03-18T19:40:12Z |
| description | We prove that a bounded 1-periodic function of a solution of a time-homogeneous diffusion equation with 1-periodic coefficients forms a process that satisfies the condition of uniform strong mixing. We obtain an estimate for the rate of approach of a certain normalized integral functional of a solution of an ordinary time-homogeneous stochastic differential equation with 1-periodic coefficients to a family of Wiener processes in probability in the metric of space $C[0, T]$. As an example, we consider an ordinary differential equation perturbed by a rapidly oscillating centered process that is a 1-periodic function of a solution of a time-homogeneous stochastic differential equation with 1-periodic coefficients. We obtain an estimate for the rate of approach of a solution of this equation to a solution of the corresponding Itô stochastic equation. |
| first_indexed | 2026-03-24T02:32:33Z |
| format | Article |
| fulltext |
UDK 519.21
B. V. Bondarev, S. M. Koz¥r\ (Donec. nac. un-t)
PEREMEÍYVANYE „PO YBRAHYMOVU”.
OCENKA SKOROSTY SBLYÛENYQ
SEMEJSTVA YNTEHRAL|NÁX FUNKCYONALOV
OT REÍENYQ DYFFERENCYAL|NOHO URAVNENYQ
S PERYODYÇESKYMY KO∏FFYCYENTAMY
S SEMEJSTVOM VYNEROVSKYX
PROCESSOV. NEKOTORÁE PRYLOÛENYQ. I
We prove that a bounded 1-periodic function of a solution of time-homogeneous diffusion equation with
1-periodic coefficients forms a process that satisfies the uniform strong intermixing condition. We
establish an estimate for the rate of approach with respect to the probability in C T0,[ ] metric of some
normed integral functional of a solution of ordinary time-homogeneous stochastic differential equation
with 1-periodic coefficients to a family of the Wiener processes. As an example, we consider an
ordinary differential equation disturbed by a rapidly oscillating centered process, which is a 1-periodic
function of a solution of time-homogeneous stochastic differential equation with 1-periodic coefficients.
An estimate for the rate of approach of a solution of this equation to a solution of the corresponding Itô
stochastic equation is established.
Dovedeno, wo obmeΩena 1-periodyçna funkciq vid rozv’qzku odnoridnoho za çasom dyfuzijnoho
rivnqnnq z 1-periodyçnymy koefici[ntamy utvorg[ proces, wo zadovol\nq[ umovu rivnomirnoho
syl\noho peremißuvannq. Vstanovleno ocinku ßvydkosti zblyΩennq za jmovirnistg v metryci
prostoru C T0,[ ] deqkoho normovanoho intehral\noho funkcionala vid rozv’qzku zvyçajnoho
odnoridnoho za çasom stoxastyçnoho dyferencial\noho rivnqnnq z 1-periodyçnymy koefici[nta-
my z sim’[g vinerovyx procesiv. Qk pryklad, rozhlqnuto zvyçajne dyferencial\ne rivnqnnq,
zburene ßvydkooscylggçym centrovanym procesom, qkyj [ 1-periodyçnog funkci[g vid
rozv’qzku odnoridnoho za çasom stoxastyçnoho dyferencial\noho rivnqnnq z 1-periodyçnymy
koefici[ntamy. Vstanovleno ocinku ßvydkosti zblyΩennq rozv’qzku takoho rivnqnnq z rozv’qz-
kom vidpovidnoho stoxastyçnoho rivnqnnq Ito.
1. Vvedenye. Yzvestno (sm., naprymer, [1 – 14]), çto pry nekotor¥x uslovyqx
centryrovann¥j sluçajn¥j process
W s dst
t
ε
ε
ε ξ= ∫ ( )
/
0
, t T∈[ ]0, ,
sblyΩaetsq (v tom yly ynom sm¥sle) pry ε → 0 s nekotor¥m semejstvom vyne-
rovskyx processov σ εW t( ) , t T∈[ ]0, , hde
σ ξ ξ=
∞
∫2 0
0
1 2
M ( ) ( )
/
t dt .
V rabotax [1, 5 – 8, 14] pryveden¥ dostatoçn¥e uslovyq dlq toho, çtob¥ sluçaj-
n¥j process Wt
ε
slabo sxodylsq pry ε → 0 k vynerovskomu processu σW t( ) ,
t T∈[ ]0, . V rabotax [2 – 4, 9 – 11] ustanovlen¥ dostatoçn¥e uslovyq dlq toho,
çtob¥ semejstvo sluçajn¥x processov Wt
ε
pry dostatoçno mal¥x ε > 0 b¥lo
„blyzko” po veroqtnosty v metryke prostranstva C T0,[ ] k vynerovskomu se-
mejstvu σ εW t( ) , t T∈[ ]0, , a ymenno ustanovlen¥ neravenstva vyda
P sup
0≤ ≤
{
t T
tW ε – σ δε εW t( ) > } < γ ε , hde funkcyy δε → 0, γ ε → 0 pry ε → 0
© B. V. BONDAREV, S. M. KOZÁR|, 2010
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6 733
734 B. V. BONDAREV, S. M. KOZÁR|
zapysan¥ v qvnom vyde. V rabotax [12, 13] pryveden¥ dostatoçn¥e uslovyq dlq
toho, çtob¥ semejstvo sluçajn¥x processov Wt
ε
pry dostatoçno mal¥x ε > 0
b¥lo „blyzko” k vynerovskomu semejstvu σ εW t( ) , t T∈[ ]0, , v sm¥sle
sup
0≤ ≤t T
tWM ε – σ εW t( ) 2 ≤ γ ε , hde funkcyq γ ε → 0 pry ε → 0 zapysana v qv-
nom vyde. V rabotax [2 – 4, 9 – 13] na process ξ( )t , t ≥ 0, lybo naklad¥valos\
uslovye ravnomernoho syl\noho peremeßyvanyq (kotoroe naz¥vagt takΩe ϕ-
peremeßyvanyem [7, s. 165] yly peremeßyvanyem „po Ybrahymovu” [15, s. 11]),
lybo yspol\zovalsq process ξ( )t , t ≥ 0, konkretnoho vyda [1]. V nastoqwej ra-
bote v kaçestve processa ξ( )t , t ≥ 0, rassmatryvaetsq reßenye odnorodnoho po
vremeny stoxastyçeskoho dyfferencyal\noho uravnenyq s peryodyçeskymy
koπffycyentamy, a ymenno, reßenye uravnenyq
ξ( )t = ξ( )0 + α ξ( )s ds
t
( )∫
0
+ β ξ( ) ( )s dW s
t
( )∫
0
, (1)
hde W s( ) — standartn¥j vynerovskyj process, ξ( )0 — v obwem sluçae slu-
çajnoe (ne zavysqwee ot W s( ) ) naçal\noe uslovye, pryçem v sylu toho, çto bu-
det yzuçat\sq process f tξ( )( ) , hde f x( ) — 1-peryodyçeskaq funkcyq, dlq
dal\nejßyx v¥kladok bez narußenyq obwnosty dostatoçno rassmatryvat\ slu-
çaj ξ( )0 ∈ 0 1,[ ) .
V dal\nejßem budem sçytat\, çto vsehda v¥polnqgtsq sledugwye uslovyq:
1) 1-peryodyçeskye koπffycyent¥ α( )x , β( )x ymegt proyzvodn¥e pervoho
porqdka ′α ( )x , ′β ( ),x udovletvorqgwye uslovyg Hel\dera;
2) funkcyy α( )x , β( )x , ′α ( )x , ′β ( ),x takov¥, çto
α α( ) ( )x x= + 1 , β β( ) ( )x x= + 1 , α( )x ≤ K < + ∞,
0 < λ ≤ β2( )x ≤ K < + ∞,
′α ( )x + ′β ( )x ≤ K < + ∞.
V kaçestve Wt
ε
budut yssledovan¥ process¥
W f s f s dst
t
ε
ε
ε ξ ξ= ( ) − ( )[ ]∫ ( ) ( )
/
M
0
, W f s f dst
t
ε
ε
ε ξ= ( ) −[ ]∫ ( )
/
0
.
Zdes\ y dalee f x( ) — dvaΩd¥ neprer¥vno dyfferencyruemaq ohranyçennaq
f x K( ) ≤ < +∞( ) 1-peryodyçeskaq funkcyq, f — ee srednee, v¥çyslennoe
po nekotoromu ynvaryantnomu raspredelenyg (sm. nyΩe formulu (12)), f tξ( )( )
— stacyonarn¥j markovskyj process. Dlq ocenky skorosty sblyΩenyq Wt
ε
s
sootvetstvugwym obrazom postroenn¥m semejstvom vynerovskyx processov
σ εW t( ) yspol\zuetsq metod odnoho veroqtnostnoho prostranstva A.FV.FSkoro-
xoda, a mera uklonenyq v prostranstve traektoryj — metryka prostranstva
C T0,[ ] . Pry postroenyy sootvetstvugwyx ocenok yspol\zuetsq martynhal\-
naq approksymacyq D.FO.FÇykyna [6]. Postroennoe martynhal\noe pryblyΩenye
pozvolylo yspol\zovat\ pry dokazatel\stve osnovnoho rezul\tata yzvestn¥e
ocenky dlq uklonenyq za uroven\ stoxastyçeskyx yntehralov v metryke
C T0,[ ] .
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
PEREMEÍYVANYE „PO YBRAHYMOVU”. OCENKA SKOROSTY SBLYÛENYQ … 735
2. Ocenka skorosty sblyΩenyq normyrovann¥x yntehralov ot dyffu-
zyonn¥x processov s peryodyçeskymy koπffycyentamy s semejstvom ne-
prer¥vn¥x martynhalov. Pust\ ρ( )x — reßenye peryodyçeskoj zadaçy
L*ρ =
1
2
2 2
2
d x x
dx
ρ β( ) ( )( )
–
d x x
dx
ρ α( ) ( )( )
= 0, ρ ρ( ) ( )x x= + 1 , (2)
odnoznaçno opredelennoe uslovyem normyrovky
ρ( )x dx =∫ 1
0
1
. (3)
Najdem reßenye zadaçy (2). Pust\ (sm. [14]) funkcyq
ϑ
α
β
( ) exp
( )
( )
x
y
y
dy
x
= −
∫
2
2
0
.
Netrudno zametyt\, çto pry x ∈[ ]0 1, dlq ϑ( )x spravedlyv¥ ocenky
0 < exp −{ }2K
λ
= C−1 ≤ ϑ( )x ≤ C = exp
2K
λ{ } < + ∞. (4)
Rassmotrym (sm. [14]) funkcyg
G x0( ) =
2
1 1
12
1
0+( )
+
∫∫ϑ β ϑ
ϑ ϑ ϑ
( ) ( ) ( )
( ) ( ) ( )
x x
y dy y dy
x
x
. (5)
Netrudno zametyt\, çto vvedennaq funkcyq G x0( ) qvlqetsq 1-peryodyçeskoj.
Dejstvytel\no, v sylu toho, çto ϑ( )x + 1 = ϑ ϑ( ) ( )x 1 , ymeem
G x0 1( )+ =
2
1 1 1
12
1
1
+( )
−
+
ϑ ϑ β ϑ
ϑ ϑ ϑ
( ) ( ) ( ) ( )
( ) ( ) ( )
x x
y dy y dy
x
∫∫∫
+
0
1x
=
=
2
1 1
1 12
00+( )
+ − ∫ϑ β ϑ
ϑ ϑ ϑ
( ) ( ) ( )
( ) ( ( ) ) ( )
x x
y dy y dy
x11
∫
= G x0( ) .
Netrudno ubedyt\sq takΩe v tom, çto funkcyq G x0( ) udovletvorqet urav-
nenyg
1
2
2
0β ( ) ( )x G x( )′ = G x x0( ) ( )α +
1
1 1
1 1
+( ) −[ ]
ϑ
ϑ
( )
( ) .
V sylu suwestvovanyq proyzvodn¥x ′α ( )x , ′β ( )x y uslovyq 0 < λ ≤ β2( )x
sleduet dyfferencyruemost\ v¥raΩenyj β2
0( ) ( )x G x( )′ y G x x0( ) ( )α . Takym
obrazom,
ρ( ) ( ) ( )x G x G y dy=
∫
−
0 0
0
1 1
(6)
qvlqetsq klassyçeskym reßenyem zadaçy (2) , udovletvorqgwym (3).
PokaΩem, çto ne narußaq obwnosty moΩno rassmatryvat\ lyß\ sluçaj,
kohda reßenye (1) startuet yz toçky
�
x ,
�
x ∈[ )0 1, . Dejstvytel\no, pust\
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
736 B. V. BONDAREV, S. M. KOZÁR|
x k k∈ +[ ), 1 , k Z∈ , Z = 0 1 1 2 2, , , , ,+ − + − …{ } ,
a
ξ x t( ) = x + α ξ x
t
s ds( )( )∫
0
+ β ξ x
t
s dW s( ) ( )( )∫
0
,
yly
ξ x t( ) =
�
x + k + α ξ x
t
s ds( )( )∫
0
+ β ξ x
t
s dW s( ) ( )( )∫
0
,
yly
ξ x t k( ) − =
�
x + α ξ x
t
s k k ds( ) − +( )∫
0
+ β ξ x
t
s k k dW s( ) ( )− +( )∫
0
.
Yz posledneho v sylu peryodyçnosty koπffycyentov α( )x , β( )x poluçaem
η( )t =
�
x + α η β η( ) ( ) ( )s ds s dW s
t t
( ) + ( )∫ ∫
0 0
,
hde η( )t = ξ x t+1( ) – k . V sylu edynstvennosty reßenyq posledneho uravnenyq
η ξ( ) ( )t tx= � , ξ ξx xt k t( ) ( )= + � ,
a v sylu peryodyçnosty f x( ) ymeem f txξ ( )( ) = f txξ � ( )( ) .
Postroym process
�
�ξ x t( ) , prynymagwyj svoy znaçenyq v polose ( , )x t{ :
0 1,[ ) × 0, +∞[ )} , plotnost\ veroqtnosty perexoda kotoroho yz toçky
�
x ∈[ )0 1,
v toçku
�
z ∈[ )0 1, za vremq t > 0 podsçyt¥vaetsq po formule [16, s. 372]
� � � � �
p x t z p x t z k
k Z
, , , ,( ) = +( )
∈
∑ .
Zdes\ p x t z
�
, ,( ) — plotnost\ veroqtnosty perexoda yz toçky
�
x ∈[ )0 1, v toçku
z ∈ −∞ +∞( ), za vremq t > 0 processa ξ �
x t( ) , startugweho v nulevoj moment
vremeny yz toçky
�
x ∈[ )0 1, . Otmetym, çto uslovyq 1, 2 harantyrugt suwestvo-
vanye plotnosty raspredelenyq p y t z( , , )
�
[8, s. 30]. Process
�
�ξ x t( ) ymeet πr-
hodyçeskoe raspredelenye s plotnost\g ρ( )x . Takym obrazom, esly v kaçestve
naçal\noho uslovyq v (1) vzqt\ ξ( )0 — ne zavysqwug ot W t( ) sluçajnug ve-
lyçynu, kotoraq ymeet plotnost\ raspredelenyq ρ( )x , to postroenn¥j v¥ße
process
�
ξ( )t s takym naçal\n¥m uslovyem budet stacyonarn¥m markovskym
processom, a znaçyt process f t
�
ξ( )( ) , a s nym y process
�η( )t = f t f
�
ξ( )( ) − = f t f t
� �
ξ ξ( ) ( )( ) − ( )M
budut stacyonarn¥my markovskymy processamy, a process
�
Wt
ε
.
=
1
ε
ξ
ε
f
t
f
�
−
=
1
ε
ξ
ε
ξ
ε
f
t
f
t� �
−
M
budet stacyonarn¥m „fyzyçeskym” bel¥m ßumom.
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
PEREMEÍYVANYE „PO YBRAHYMOVU”. OCENKA SKOROSTY SBLYÛENYQ … 737
Netrudno takΩe zametyt\, çto dlq 1-peryodyçeskoj funkcyy f x( ) spra-
vedlyvo sledugwee [16, s. 372]:
M f txξ �( )( ) = f y p x t y dy( ) ( , , )
−∞
+∞
∫ �
= f y p x t y dy
k
k
k
( ) ( , , )
+
=−∞
+∞
∫∑
1
�
=
= f y p x t y k dy
k
( ) ( , , )
� � � �
0
1
∫ ∑ +
=−∞
+∞
= f y p x t y dy f tx( ) ( , , ) ( )
� � � � � �
�
0
1
∫ = ( )M ξ .
Pust\ 0 < t1 < t2 < … < tn < + ∞, tohda
ϕξ ( , , , )z z zn1 2 … = M exp ( )iz f tk k
k
n
ξ( )
=
∑
1
=
= exp ( ) ( ) , ,iz f x x p x t xk k
k
n
=
∑∫
( )
00
1
0 0 1 1ρ � �
−−∞
+∞
∫ …
… p x t t x dx dx dx dxn n n n n n− −
−∞
+∞
−−( ) …∫ 1 1 1 1 0, ,
�
=
= exp ( ) ( ) , ,iz f x x p x t xk k
k
n
=
∑∫
( )
00
1
0 0 1 1ρ � �
kk
k
k
+
=−∞
+∞
∫∑
1
…
… p x t t x dx dx dx dn n n n n
k
k
k
n− −
+
=−∞
+∞
−−( ) …∫∑ 1 1
1
1 1, ,
��
x0 =
= exp ( ) ( ) , ,iz f x x p x t xk k
k
n � � � �
=
∑∫
00
1
0 0 1 1ρ ++( )∫∑
=−∞
+∞
k
k
1
0
1
1
…
… p x t t x k dx dxn n n n n n
k
n
n
− −
=−∞
+∞
−− +( )∫∑ 1 1
0
1
1, ,
� � � …… dx dx
� �
1 0 =
= exp ( ) ( ) , ,iz f x x p x t xk k
k
n � � � � �
=
∑∫
00
1
0 0 1ρ 11
0
1
( )∫ …
…
� � � � � �
p x t t x dx dx dx dxn n n n n n− − −−( ) …∫ 1 1
0
1
1 1 0, , =
= M exp ( )iz f tk k
k
n �
ξ( )
=
∑
1
= ϕξ
� ( , , , )z z zn1 2 … ,
t.Fe. xarakterystyçeskye funkcyy koneçnomern¥x raspredelenyj sovpadagt, a
znaçyt, koneçnomern¥e raspredelenyq u processov
�η( )t = f t f
�
ξ( )( ) − = f t f t
� �
ξ ξ( ) ( )( ) − ( )M
y
η( )t = f t fξ( )( ) − = f t f tξ ξ( ) ( )( ) − ( )M
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
738 B. V. BONDAREV, S. M. KOZÁR|
odny y te Ωe. Otsgda sleduet, çto process
Wt
ε
.
=
1
ε
ξ εf t f/( )( ) −[ ] =
1
ε
ξ ε ξ εf t f t/ /( )( ) − ( )( )[ ]M
takΩe budet stacyonarn¥m „fyzyçeskym” bel¥m ßumom.
Yzvestno [16, s. 370, 373], çto esly α( )x , β( )x — 1-peryodyçeskye koπffy-
cyent¥ uravnenyq (1) — ymegt proyzvodn¥e pervoho porqdka ′α ( )x , ′β ( )x ,
udovletvorqgwye uslovyg Hel\dera, y v¥polneno uslovye 0 < λ ≤ β2( )x ≤ K <
< + ∞, to dlq lgboj ohranyçennoj 1-peryodyçeskoj funkcyy f x( ) spravedly-
va ocenka
sup ( )
x
xf t fM ξ( ) − ≤ c f x t
x
sup ( ) exp −{ }γ , (7)
hde postoqnn¥e c > 0, γ > 0 opredelqgtsq çerez koπffycyent¥ uravnenyq (1),
ξ x t( ) — reßenye uravnenyq
ξ x t( ) = x + α ξ x
t
s ds( )( )∫
0
+ β ξ x
t
s dW s( ) ( )( )∫
0
,
postoqnnaq f podsçyt¥vaetsq po formule
f f x x dx= ∫ ( ) ( )ρ
0
1
, (8)
ρ( )x opredeleno v (6).
Pust\ ς y t( ) = f txξ ( )( ) , t ≥ 0, — process s naçal\n¥m uslovyem y f x= ( ) ,
I yA( ) — yndykator proyzvol\noho mnoΩestva A yz oblasty znaçenyj ς y t( ) .
Tohda
I t I f t g tA y A x A xς ξ ξ( ) ( ( ) ( )( ) = ( ) = ( ) ,
hde g xA( ) = I f xA ( )( ) — takΩe ohranyçennaq 1-peryodyçeskaq funkcyq, dlq
kotoroj spravedlyvo sootnoßenye (7), kotoroe v dannom sluçae prynymaet vyd
sup ( ) ( ) ( )
,y A
A y AI t I f x x dxM ς ρ( ) − ( )∫
0
1
≤ c texp −{ }γ .
Esly π( )A — mera, opredelennaq sootnoßenyem
π ρ( ) ( )
: ( )
A x dx
x f x A
=
∈{ }
∫ ,
to ymeem
sup , , ( )
,y A
y t A AP{ } − π = sup ( ) ( ) ( )
,y A
A y AI t I f x x dxM ς ρ( ) − ( )∫
0
1
≤
≤ c texp −{ }γ ,
t.Fe. v¥polnqetsq uslovye (19.1.7) yz [17], dostatoçnoe dlq toho, çtob¥ process
f tξ( )( ) (naçal\noe uslovye raspredeleno s plotnost\g ρ( )x ) udovletvorql us-
lovyg ravnomernoho syl\noho peremeßyvanyq s koπffycyentom peremeßyva-
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
PEREMEÍYVANYE „PO YBRAHYMOVU”. OCENKA SKOROSTY SBLYÛENYQ … 739
nyq, ne prev¥ßagwym 2c texp −{ }γ . Takym obrazom, klass sluçajn¥x proces-
sov, kotor¥j stroytsq kak superpozycyq 1-peryodyçeskoj funkcyy ot reßenyq
dyffuzyonnoho uravnenyq s 1-peryodyçeskymy koπffycyentamy, budet pere-
meßyvat\sq „po Ybrahymovu”. Kak pokaz¥vagt pryvedenn¥e nyΩe prymer¥, πto
ves\ma ßyrokyj klass.
Rassmotrym funkcyg
U x f t f dtx( ) ( )= − ( ) −[ ]
+∞
∫ M ξ
0
, (9)
hde
ξ x t( ) = x + α ξ x
t
s ds( )( )∫
0
+ β ξ x
t
s dW s( ) ( )( )∫
0
, (10)
a f x( ) — dvaΩd¥ neprer¥vno dyfferencyruemaq ohranyçennaq f x( )( ≤ K <
< +∞) 1-peryodyçeskaq funkcyq (v sylu uslovyq (7) yntehral v (9) opredelen).
PokaΩem, çto U x( ) — 1-peryodyçeskaq funkcyq, kotoraq qvlqetsq reßenyem
uravnenyq
β2 2
22
( )
( )
x d U
dx
x + α( ) ( )x
dU
dx
x = f x f( ) −[ ] . (11)
Ustanovym peryodyçnost\ funkcyy U x( ) . Pust\ x ∈ k k, +[ )1 , k Z∈ , Z —
mnoΩestvo cel¥x çysel, a ξ x t( ) — reßenye uravnenyq (10). Narqdu s (10) ras-
smotrym uravnenye
ξ x t+1( ) = x + 1 + α ξ x
t
s ds+( )∫ 1
0
( ) + β ξ x
t
s dW s+( )∫ 1
0
( ) ( ) .
Yz posledneho v sylu peryodyçnosty koπffycyentov α( )x , β( )x ymeem
η( )t = x + α η( )s ds
t
( )∫
0
+ β η( ) ( )s dW s
t
( )∫
0
, (12)
hde η( )t = ξ x t+1( ) – 1. V sylu edynstvennosty reßenyq (10) yz (12) sleduet
η ξ( ) ( )t tx= , ξ ξx xt t+ = +1 1( ) ( ) ,
a v sylu peryodyçnosty f x( ) ymeem f txξ +( )1( ) = f txξ ( )( ) , otkuda v sylu
predstavlenyq (9) sleduet peryodyçnost\ U x( ) . Dalee, pust\
V t x f t fx( , ) ( )= − ( ) −[ ]M ξ ,
tohda (sm. [18]) funkcyq V t x( , ) qvlqetsq reßenyem zadaçy
β2 2
22
( )
( , )
x V
x
t x
∂
∂
+ α( ) ( , )x
V
x
t x
∂
∂
=
∂
∂
V
t
t x( , ) ,
(13)
V x f x f( , ) ( )0 = − −[ ] .
Yntehryruq obe çasty (13) po t v predelax ot 0 do T y perexodq k predelu pry
T → + ∞, s uçetom ocenky (7) ymeem
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
740 B. V. BONDAREV, S. M. KOZÁR|
β2 2
22
( )
( )
x U
x
x
∂
∂
+ α( ) ( )x
U
x
x
∂
∂
= lim
T
T
V
t
t x dt
→+∞
∂
∂∫ ( , )
0
=
= −
→+∞
lim
T
V T x( , ) + f x f( ) −[ ] = − −[ ]
→+∞
lim M
T
xf T f( ( ))ξ +
+ f x f( ) −[ ] = f x f( ) −[ ] ,
t.Fe. (11) ymeet mesto.
Yz (9) vsledstvye (7) sleduet ohranyçennost\ U x( ) . Dejstvytel\no,
U x( ) ≤ M f t f dtx( ( ))ξ −[ ]
+∞
∫
0
≤ Kc t dtexp −{ }
+∞
∫ γ
0
=
Kc
γ
. (14)
Oboznaçym ψ( )x =
dU
dx
, tohda yz (11) sleduet, çto ψ( )x qvlqetsq reßenyem
zadaçy
d
dx
x
x
x
ψ α
β
ψ+
2
2
( )
( )
( ) =
2
2
f x f
x
( )
( )
−[ ]
β
, ψ ψ( ) ( )x x+ =1 . (15)
Netrudno ubedyt\sq v tom, çto reßenyem zadaçy (15) budet funkcyq
ψ( )x = −
−[ ]
− ∫ϑ ϑ
β
1
2
1 2
( ) ( )
( )
( )
x y
f y f
y
dy
x
. (16)
V sylu peryodyçnosty ψ( )x y (4) ymeem ocenku
ψ
λ ψ( )x
C
K D≤ =
4 2
. (17)
Pust\ U x( ) — reßenye zadaçy (11). Tohda, prymenqq formulu Yto k processu
U txξ ( )( ) , poluçaem
dU txξ ( )( ) = LU t dtxξ ( )( ) + β ξ ψ ξx xt t dW t( ) ( ) ( )( ) ( ) .
Otsgda v sylu (11) sleduet
dU txξ ( )( ) = f t f dtxξ ( )( ) −[ ] + β ξ ψ ξx xt t dW t( ) ( ) ( )( ) ( ) .
Yntehryruq poslednee uravnenye v predelax ot 0 do t /ε , ymeem
ε ξ
ε
f s f dsx
t
( ( ))
/
−[ ]∫
0
= − ( ) −[ ]ε ξ εU t U xx ( / ) ( ) –
– ε β ξ ψ ξ
ε
x x
t
s s dW s( ) ( ) ( )
/
( ) ( )∫
0
. (18)
Yz (18) sleduet ravenstvo
ε ξ ξ
ε
f s f s dsx x
t
( ) ( )
/
( ) − ( )[ ]∫ M
0
= − ( ) −[ ]ε ξ εU t U xx ( / ) ( ) –
– ε β ξ ψ ξ
ε
x x
t
s s dW s( ) ( ) ( )
/
( ) ( )∫
0
– ε ξ
ε
M f s f dsx
t
( )
/
( ) −[ ]∫
0
.
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
PEREMEÍYVANYE „PO YBRAHYMOVU”. OCENKA SKOROSTY SBLYÛENYQ … 741
Netrudno zametyt\, çto predstavlenye (18) — πto predstavlenye D.FO.FÇyky-
naF[6]: v dannom sluçae
ρε
t = ε ξ εU x U tx( ) ( / )− ( )[ ], µε
t = − ( ) ( )∫ε β ξ
ξε
x
t
xs
dU s
dx
dW s( )
( )
( )
/
0
.
Takym obrazom, spravedlyva sledugwaq teorema.
Teorema 1. Pust\ dyffuzyonn¥j process zadan kak reßenye uravnenyq (1)
y v¥polnen¥ uslovyq 1, 2. Tohda dlq lgboj 1-peryodyçeskoj dvaΩd¥ nepre-
r¥vno dyfferencyruemoj funkcyy f x( ) f x K( ) ≤ < +∞( ) y lgboho 0 < ε ≤
1 spravedlyva ocenka
sup ( ) ( ) ( )
0 ≤ ≤
( ) −[ ] + ( ) ( )
t T
x x xf s f ds s s dWε ξ ε β ξ ψ ξ (( )
//
s
tt
00
εε
∫∫ ≤ ε
γ
2 Kc
,
(19)
hde postoqnn¥e c > 0, γ > 0 vzqt¥ yz ocenky (7), funkcyq ψ( )x zadaetsq
formuloj (16), a ρ( )x — formuloj (6), v kotoroj G x0( ) zadano v (5).
Zameçanye 1. Vospol\zovavßys\ ocenkamy (19) y (7), netrudno poluçyt\
ocenku
sup ( ) ( ) ( )
0 ≤ ≤
( ) − ( )[ ] + ( )
t T
x x xf s f s ds sε ξ ξ ε β ξ ψ ξM xx
tt
s dW s( ) ( )
//
( )∫∫
00
εε
≤
≤ ε
γ
2 Kc
+ ε ξ
ε
Mf s f dsx
T
( )
/
( ) −∫
0
≤ ε
γ
2 Kc
+
+ Kc t dt
T
ε γ
ε
exp
/
−{ }∫
0
≤ ε
γ
3 Kc
.
3. Ocenka skorosty sblyΩenyq semejstva normyrovann¥x stoxastyçes-
kyx yntehralov ot dyffuzyonn¥x processov s peryodyçeskymy koπffy-
cyentamy s semejstvom vynerovskyx processov. Osnovn¥m rezul\tatom πto-
ho punkta qvlqetsq sledugwaq teorema.
Teorema 2. Pust\ ρ( )x — plotnost\ raspredelenyq, kotoraq zadaetsq
formuloj (6), dyffuzyonn¥j process zadan kak reßenye uravnenyq (1) s na-
çal\n¥m znaçenyem ξ( )0 , ne zavysqwym ot W t( ) , t ≥ 0 ymegwym raspredele-
nye s plotnost\g ρ( )x , v¥polnen¥ uslovyq 1, 2, y
ψ β ρ2 2
0
1
( ) ( ) ( )x x x dx∫ = σ2 0> .
Tohda dlq lgboho 0 < σ < 1 4/ spravedlyva ocenka
P sup ( ) ( ) ˜ ( )
/
0 0≤ ≤
( ) − ( )[ ] + >
≤∫
t T
t
f s Mf s ds W tε ξ ξ σ δ γε
ε
ε ε, (20)
hde
�W tε ( ) — nekotoroe semejstvo standartn¥x vynerovskyx processov,
δ ε ε ε
γε
δ γ ε δ
= + +( ) +− −
6 12
41 4
T ce
Kc/ /
,
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
742 B. V. BONDAREV, S. M. KOZÁR|
γ ε = 20 1
32
8
2
3 1 4
T
K
Kε
λ
λ
ε δ
+
− { }
−
exp
exp /
+
+ 4
2
2
1 2 2
2
2exp /−
−
σ
ε δ TD
+
+F exp /
/
−
+ +
−
1
256
1
1
2 2
11 2
1 2
K
T
ε εδ
+
T
ce
ε
γ ε δ
+
− −
1 12
1 4/ /
,
(21)
postoqnn¥e c > 0, γ > 0 vzqt¥ yz ocenky (7), a
D2 =
16
4 2exp
K
cK K
λ
λγ
{ }
+
4 2 2
2
K c
γ
.
Dokazatel\stvo. Budem sledovat\ sxeme rassuΩdenyj yz [3, 4]. Snaçala
otmetym, çto spravedlyva ocenka
P sup ( ) ( ) ( )
t t h t
s s dW s x
≤ ≤ +
( ) ( ) >
∫
τ
τ
ε ψ ξ β ξ
≤ 2
2
2
2exp −
x
hKDε ψ
, (22)
hde postoqnnaq Dψ opredelena v (17).
V spravedlyvosty (22) netrudno ubedyt\sq, esly vospol\zovat\sq πksponen-
cyal\noj ocenkoj dlq supremuma neprer¥vnoho martynhala µ( )t [19, s. 173],
zametyv, çto v dannom sluçae ymeet mesto ocenka εµ εµ,
t
t h+
≤ ε ψhKD2
.
Pust\
ηε ( )t = ε ψ ξ β ξ
ε
( ) ( ) ( )
/
s s dW s
t
( ) ( )∫
0
,
ςε ( )t = ε ξ ξ
ε
f s f s ds
t
( ) ( )
/
( ) − ( )[ ]∫ M
0
= ε ξ
ε
f s f ds
t
( )
/
( ) −[ ]∫
0
.
V sylu toho, çto
ς ε ξ ξ
ε
ηε ε( ) ( ) ( )t U U
t
t= ( ) −
−0 ,
s uçetom (7) y (14) pry τ ≥ t ymeem ocenku
ς τ ςε ε( ) ( )− t ≤ ε
γ
2Kc
+ η τ ηε ε( ) ( )− t .
S uçetom posledneho y ocenky (22) netrudno ubedyt\sq v tom, çto ymeet mesto
neravenstvo
P sup ( ) ( )
t t h
t x
Kc
≤ ≤ +
− > +
τ
ε ες τ ς ε
γ
2
≤ 2
2
2
2exp −
x
hKDε ψ
. (23)
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
PEREMEÍYVANYE „PO YBRAHYMOVU”. OCENKA SKOROSTY SBLYÛENYQ … 743
Pust\ lε = o
1
ε
→ ∞, ε → 0, l
T
ε ε
< , n =
T
lε ε
— celaq çast\
T
lε ε
, vremenn¥e
otrezky bε , hε takye, çto
T
nl r
ε ε ε= + , l b hε ε ε= + , hε = o l( )ε → ∞, ε → 0,
— ynterval¥ dlq razbyenyq S.FN.FBernßtejna (sm., naprymer, [4]). Ydeq raz-
byenyq Bernßtejna sostoyt v tom, çto summa sluçajn¥x velyçyn razbyvaetsq
na dve çasty: na osnovnug summu (no uΩe so slabozavysym¥my slahaem¥my) y
prenebreΩymug çast\, kotoraq po veroqtnosty budet stremyt\sq k nulg. Vve-
dem oboznaçenyq
νε
k = ε ψ ξ β ξ
ε ε
ε
( ) ( ) ( )s s dW s
kl b
kl
( ) ( )
−
∫ , λε
k = ε ψ ξ β ξ
ε
ε
( ) ( ) ( )
( )
s s dW s
k l
kl
( ) ( )
−
∫
1
,
µε
k = ε ψ ξ β ξ
ε
ε ε
( ) ( ) ( )
( )
( )
s s dW s
k l
k l h
( ) ( )
−
− +
∫
1
1
,
αε
k = ε ξ ξ
ε
ε ε
f s f s ds
k l
k l h
( ) ( )
( )
( )
( ) − ( )[ ]
−
− +
∫ M
1
1
,
βε
k = f s f s ds
kl b
kl
ξ ξ
ε ε
ε
( ) ( )( ) − ( )[ ]
−
∫ M , γ α ε βε ε ε
k k k= + , k = 1, 2, … , n.
Dalee, pust\ η1 , η2 , … — posledovatel\nost\ sluçajn¥x velyçyn, udovletvo-
rqgwyx uslovyg Mηk = 0, Dηk < + ∞, 0 = t0 < t1 < … < tk−1 < tk < …F— toç-
ky na vremennoj osy, η( )0 = 0, η( )k = ηii
k
=∑ 1
, k = 1, 2, … . Par¥ t kk , ( )η( ) , k =
= 0, 1, … , budem naz¥vat\ uzlamy. Budem rassmatryvat\ sluçajn¥e stupençat¥e
funkcyy vyda
η( )t = η( )k − 1 , η( )0 = 0 pry t ∈F[ , )t tk k−1 , k = 1, 2, … .
Pust\ s tε
1( ) — sluçajnaq stupençataq funkcyq s uzlamy
k l i
i
k
ε γε
ε,
=
∑
1
, k = 0, 1, … , n, =
=
∑ 0
1
0
i
,
hde n =
T
lε ε
— celaq çast\
T
lε ε
. Tohda na vremennom otrezke k lε ε[ , (k +
+ 1) ε εl ) spravedlyv¥ ocenky
sup ( ) ( )
( )k l t k l
t t
ε ε
ε ε
ε ε
ς ς
≤ ≤ +
−
1
1 ≤ ε ς ς ε
ε ε
ε ε ε
ε ε
sup ( ) ( )
( )k l t k l
t k l
≤ ≤ +
−
1
,
(24)
αε
k ≤ ε ς ς ε
ε ε ε
ε ε ε
ε ε ε
sup ( ) ( )
( ) ( )k l t k l h
t k l
− ≤ ≤ − +
− −
1 1
1(( ) .
Yspol\zuq pervug yz ocenok (24), s uçetom ocenky (23) poluçaem
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
744 B. V. BONDAREV, S. M. KOZÁR|
P sup ( ) ( )
( )k l t k l
t t x
Kc
ε ε
ε ε
ε ε
ς ς ε
γ≤ ≤ +
− > +
1
1
1
2
≤ 2
2
1
2
2exp −
x
l KDε ε ψ
.
S uçetom πtoj ocenky ymeem
P sup ( ) ( )
0
1
1
2
≤ ≤
− > +
t T
t t x
Kc
ς ς ε
γε ε ≤
≤ − >
≤ ≤ ≤ ≤ +
P max sup ( ) ( )
( )0 1
1
1
k n k l t k l
t t x
ε ε
ε ε
ε ε
ς ς ++
ε
γ
2 Kc
≤
≤ 2 1
2
1
2
2
T
l
x
l KDε εε ε ψ
+
−
exp . (25)
Pust\ ςε
2( )t — sluçajnaq stupençataq funkcyq s uzlamy
k l i
i
k
ε ε βε
ε,
=
∑
1
, k = 0, … , n, =
=
∑ 0
1
0
i
.
Tohda, yspol\zuq vtorug yz ocenok (24), s uçetom (23) poluçaem
P sup ( ) ( )
0
2 1
2
2
≤ ≤
− > +
t T
t t x
Kc
ς ς ε
γε ε ≤
≤ P max
1 1
2
2
≤ ≤ =
∑ > +
k n
i
i
k
x
Kcα ε
γ
ε ≤ P α ε
γ
ε
i
i
n
x
Kc
> +
=
∑ 2
1
2
≤
≤ 2 1
2
2
2
2
T
l
x
h KDε εε ε ψ
+
−
exp . (26)
Yz (25) y (26) sleduet ocenka
P sup ( ) ( )
0
2
1 2
4
≤ ≤
− > + +
t T
t t x x
Kc
ς ς ε
γε ε ≤
≤ 2 1
2
1
2
2
T
l
x
l KDε εε ε ψ
+
−
exp + 2 1
2
2
2
2
T
l
x
h KDε εε ε ψ
+
−
exp .
Yz posledneho pry x x1 2= ymeem ocenku
P sup ( ) ( )
0
2
12
4
≤ ≤
− > +
t T
t t x
Kc
ς ς ε
γε ε ≤ 4 1
2
1
2
2
T
l
x
l KDε εε ε ψ
+
−
exp .
(27)
Otmetym, çto uzl¥ u lomanoj ςε
2( )t postroen¥ po summam slabozavysym¥x ve-
lyçyn. V dal\nejßem nam ponadobytsq analoh lomanoj ςε
2( )t , no uΩe s uzla-
my, postroenn¥my po summam nezavysym¥x velyçyn. Dejstvytel\no, uslovye (7)
dostatoçno dlq toho, çtob¥ posledovatel\nost\ βε
i{ } , i = 1, 2, … , peremeßyva-
las\ „po Ybrahymovu”, pryçem v sylu toho, çto sluçajn¥e velyçyn¥ βε
1{ , …
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
PEREMEÍYVANYE „PO YBRAHYMOVU”. OCENKA SKOROSTY SBLYÛENYQ … 745
… , βε
n} otstoqt druh ot druha po vremeny ne menee çem na velyçynu hε , σ-al-
hebra ℑ1
khε
, poroΩdennaq velyçynamy βε
i{ } , i = 1, … , k, y σ-alhebra, poroΩ-
dennaq velyçynamy ℑ +kh h
nh
ε ε
ε , takΩe otstoqt po vremeny druh ot druha ne menee
çem na velyçynu hε . Tohda dlq koπffycyenta peremeßyvanyq „po Ybrahymo-
vu” ϕ ε( )h spravedlyva ocenka [17, s. 467]
ϕ γε ε( ) exph c h≤ −{ }2 . (28)
Pust\ vektor
� �β βε ε
1 , ,…{ }n sostoyt yz nezavysym¥x sluçajn¥x velyçyn
�βε
i ,
i = 1, … , n, kaΩdaq yz kotor¥x ymeet takoe Ωe raspredelenye, kak y βε
i , i =
= 1, … , n. Pust\ ςε
3( )t — sluçajnaq stupençataq funkcyq s uzlamy
k l i
i
k
ε ε βε
ε, �
=
∑
1
, =
=
∑ 0
1
0
i
, k = 0, … , n.
Yzvestno [21], çto v sluçae ravnomernoho syl\noho peremeßyvanyq spravedlyva
ocenka
P β β ϕ ϕε ε
ε εk k h h− ≥{ } ≤� 6 6( ) ( ) , k = 1, 2, … , n.
Yspol\zuq πtu ocenku y ocenku (28), ubeΩdaemsq v tom, çto v¥polnqetsq ne-
ravenstvo
P sup ( ) ( )
0
3 2 12 1
≤ ≤
−− ≥ +
t T
ht t ce
T
l
ς ς ε
εε ε
γ
ε
ε
≤
≤ P max ( )
1 1 11
12 1
≤ ≤ + ==
−− ≥ +∑∑
k n
i i
i
k
i
k
hce nβ βε ε γ ε�
≤
≤ P β βε ε γ ε
i i
i
n
hce n− ≥ +
=
−∑ �
1
12 1( ) ≤
≤ P β β
ε
ε ε γ
ε
ε
i i
h
i
n
ce
T
l
ce− ≥{ } ≤ +
−
=
−∑ � 12 1 12
1
γγ εh . (29)
Postroym analoh lomanoj ςε
3( )t , no uΩe s uzlamy, postroenn¥my po summam
nezavysym¥x normal\no raspredelenn¥x velyçyn.
Pust\
� �β βε ε
1 , ,…{ }n — vektor, sostoqwyj yz nezavysym¥x sluçajn¥x vely-
çyn, a vektor φ φε ε
1 , ,…{ }n sostoyt yz nezavysym¥x normal\no raspredelenn¥x
sluçajn¥x velyçyn, ymegwyx, kak y velyçyn¥
�βε
1 , … , �βε
n , nulevoe srednee y
ravn¥e vtor¥e moment¥, t.Fe.
M Mφ βε ε
i i= ˜ 0 , M M Mφ β βε ε ε
i i i[ ] = [ ] = [ ]2 2 2˜ , i = 1, … , n.
V postroenyqx A.FY.FSaxanenko [21 – 23] po φε
n = φ φε ε
1 , ,…{ }n — vektoru yz ne-
zavysym¥x normal\no raspredelenn¥x velyçyn — stroylsq
��βε
n = �� ��β βε ε
1 , ,…{ }n
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
746 B. V. BONDAREV, S. M. KOZÁR|
— vektor yz nezavysym¥x velyçyn, ymegwyx to Ωe samoe fyksyrovannoe ras-
predelenye, çto y ysxodn¥j vektor
� �β βε ε
1 , ,…{ }n , no naybolee blyzkyj k vekto-
ru φε
n . Ymeet mesto y obratnoe postroenye (sm. [24]), kohda po ysxodnomu vek-
toru
� �β βε ε
1 , ,…{ }n stroytsq vektor φε
n = φ φε ε
1 , ,…{ }n . Zametym, çto s veroqt-
nost\g 1 βε
k ≤ 2 Kbε (tohda y
�βε
k ≤ 2 Kbε s veroqtnost\g 1), a v sylu
sledstvyq 1 yz [23] uslovye
α β α β βε ε εM D˜ exp ˜ ˜
k k k
3 { } ≤ , k = 1, … , n,
v¥polnqetsq s α = ( )4 1Kbε
−
.
Yz rezul\tatov rabot¥ [24] (lemma 1.5) sleduet, çto moΩno zadat\ sluçaj-
n¥e velyçyn¥
�βε
1 , … , �βε
n , voobwe hovorq, na bolee bohatom veroqtnostnom
prostranstve ′ ′ℑ ′( )Ω , , P y po πtoj posledovatel\nosty na veroqtnostnom pros-
transtve ′ ′ℑ ′( )Ω , , P postroyt\ posledovatel\nost\ φε
1 , … , φε
n nezavysym¥x
normal\no raspredelenn¥x sluçajn¥x velyçyn takyx, çto
′ = =M M�β φε ε
i i 0 y ′ =D D�β φε ε
i i
dlq vsex i, pryçem budet v¥polnqt\sq neravenstvo
′ { }M exp αc n∆ ≤ 1 + αBn , ∆n = max
1 1 1≤ ≤ = =
∑ ∑−
k n
i
i
k
i
i
k
�β φε , (30)
hde c > 0 — nekotoraq absolgtnaq postoqnnaq, Bn
2 = ′=∑ D β̃ε
kk
n
1
≤ 2 2 2nK bε .
Ne umen\ßaq obwnosty (sm. [23]) moΩno sçytat\, çto 0 < c ≤
1
64
.
V teoreme Bekeßa – Fylyppa trebuetsq, çtob¥ prostranstvo, na kotorom za-
dagtsq sluçajn¥e velyçyn¥, b¥lo dostatoçno bohat¥m; v protyvnom sluçae
rassuΩdenyq provodqtsq na bolee bohatom prostranstve. ∏to obæqsnqetsq tem,
çto dal\nejßye postroenyq provodqtsq çerez ravnomerno raspredelennug slu-
çajnug velyçynu, kotorug nel\zq, naprymer, zadat\ na prostranstve s atomamy
Ω = ω1{ , ω2 , … , ωn} (to Ωe samoe kasaetsq postroenn¥x v dal\nejßem nor-
mal\no raspredelenn¥x velyçyn).
M¥ yznaçal\no budem predpolahat\, çto ysxodnoe prostranstvo dostatoçno
bohatoe, tohda vse postroenyq moΩno v¥polnyt\ na ysxodnom prostranstve.
Pust\ ςε
4 ( )t — sluçajnaq stupençataq funkcyq s uzlamy
k l i
i
k
ε ε φε ,
=
∑
1
, =
=
∑ 0
1
0
i
, k = 0, … , n.
Tohda, yspol\zuq neravenstvo (30), ymeem ocenku
P sup ( ) ( )
0
4 3
3
≤ ≤
− >{ }
t T
t t xς ςε ε ≤
1
64 641 1 1
3max
≤ ≤ = =
− >
∑ ∑
k n
i
i
k
i
i
k x�β φ
ε
ε ≤
≤ exp exp−
x
K b K b
n
3
256
1
256ε εε ε
M ∆ ≤
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
PEREMEÍYVANYE „PO YBRAHYMOVU”. OCENKA SKOROSTY SBLYÛENYQ … 747
≤ exp
/
−
+ +
x
K b
T
l
3
1 2
256
1
1
2 2
1
ε εε ε
.
V sylu toho, çto
βε
k = −νε
k + ε ξ ξε ε εU k l h U kl(( ) ( )− +( ) − ( )[ ]1 ,
poluçaem
M Mβ νε ε
k k[ ] − [ ]2 2
≤ M ν ε
γ
ε
k
Kc ( )2 1 2 4/
+ ε
γ
4 2 2
2
K c
≤
≤ ε
γε ψb D K
Kc4
+ ε
γ
4 2 2
2
K c
= ε εb D1 , (31)
hde
D1 =
16 2 2C cK K
λγ
+
4 2 2
2
K c
γ
,
a poskol\ku
M ν ε σε
εk b =
2 2 , k = 1, … , n, (32)
yz (31) y (32) ymeem ocenku
Mεφ ε σεk b2 2− ≤ ε εb D2 , k = 1, … , n, (33)
hde
D2 =
16
4 2exp
K
cK K
λ
λγ
{ }
+
4 2 2
2
K c
γ
.
Yz (33) poluçaem
M φ ε σε
ε
ε ε
k
k
T l
b[ ] −
=
[ ]
∑ 2 2
2
1
/
≤ ε
εε
ε
2
2
2b D
T
l
≤ εTD2
2 . (34)
Oboznaçyv
�φk =
φ
φ
k
kM 2
, postroym sluçajnug stupençatug funkcyg ςε
5( )t s
uzlamy
k l b i
i
k
ε ε σ φε ε, 2
1
�
=
∑
, =
=
∑ 0
1
0
i
, k = 0, … , n.
Yspol\zuq ocenku dlq maksymuma summ nezavysym¥x normal\no raspredelen-
n¥x sluçajn¥x velyçyn [25, s. 67], naxodym
P sup ( ) ( )
0
4 5
4
≤ ≤
− >{ }
t T
t t xς ςε ε ≤ 4 2 2
4
1
P M b xi i
i
n
εφ ε σ φε−
>
=
∑ � ≤
≤ 4
2
4
2
2
2 2 2
1
exp exp−{ } −
=
∑zx
z
b
bi
i
n
M M
ε σ
εφ ε σ
ε
ε
. (35)
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
748 B. V. BONDAREV, S. M. KOZÁR|
Yz (35) s uçetom ocenky (34) poluçaem
P sup ( ) ( )
0
4 5
4
≤ ≤
− >{ }
t T
t t xς ςε ε ≤ 4
2
4
2
2
2
2exp − +
zx
z TD
bεσ
. (36)
Mynymyzyruq pravug çast\ (36) po z > 0, ymeem ocenku
P sup ( ) ( )
0
4 5
4
≤ ≤
− >{ }
t T
t t xς ςε ε ≤ 4
2
4
2 2
2
2exp −
x b
TD
εσ
. (37)
Poskol\ku v sylu rezul\tatov rabot¥ [26] suwestvuet standartn¥j vynerov-
skyj process W tε ( ) , t ≥ 0, takoj, çto dlq lgboj
�φ ε σεi b 2
, i = 1, … , n, ymeet
mesto predstavlenye
ε σ φεb i
2 � = W i bε εε σ2( ) – W i bε εε σ−( )( )1 2 , i = 1, … , n,
oboznaçaq çerez ηε
6( )t sluçajnug stupençatug funkcyg s uzlamy
k l W k bε ε σε ε ε, 2( )( ) , k = 0, … , n,
s uçetom upomqnutoho predstavlenyq y (37) ubeΩdaemsq v spravedlyvosty
ocenky
P sup ( ) ( )
0
6 3
3 4
≤ ≤
− > +{ }
t T
t t x xς ςε ε ≤
≤ exp
/
−
+ +
x
K b
T
l
3
1 2
256
1
1
2 2
1
ε εε ε
+ −
4
2
4
2 2
2
2exp
x b
TD
εσ
. (38)
Pust\ teper\ ηε
7( )t — sluçajnaq stupençataq funkcyq s uzlamy
k l W k lε ε σε ε ε, ⋅( )( )2 , k = 0, … , n.
V sylu toho, çto dlq normal\noj N (0, 1) velyçyn¥ ξ v¥polnqetsq nera-
venstvo
P ξ ≥{ }x ≤ 2
2
2
exp −
x
,
yspol\zuq neravenstvo dlq summ nezavysym¥x symmetryçn¥x sluçajn¥x vely-
çyn [25], poluçaem ocenku
P sup ( ) ( )
0
7 6
5
≤ ≤
− >{ }
t T
t t xς ςε ε ≤ P max ( ) ( )
1
2 2
5≤ ≤
− >{ }k n
W k b W k l xε ε ε εε σ ε σ ≤
≤ P max ( )
1
2
5≤ ≤
>{ }k n
W k h xε εε σ ≤ 4 2
5P W n h xε εε σ( ) >{ } ≤
≤ 4 2
5P W
Th
l
xε
ε
ε
σ
>
= 4 1 5P W x
l
Th
ε
ε
ε
( ) >
≤
≤ 8
2
5
2
2exp −
( )
x
TKD h lψ ε ε/
. (39)
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
PEREMEÍYVANYE „PO YBRAHYMOVU”. OCENKA SKOROSTY SBLYÛENYQ … 749
Pust\ W tε σ( )2 = σ ε�W t( ) , hde
�W tε ( ) = W tε σ σ( )/2
— standartn¥j vynerovskyj
process. Tohda ymeet mesto ocenka
P sup ( ) ( )
0
7
6
≤ ≤
− >{ }
t T
W t t xσ ςε ε� ≤
≤ P max sup ( ) ( )
( )1 1
2 1
≤ ≤ − ≤ ≤
− −
k n k l t k l
W t W k
ε ε
ε ε
ε ε
σ εll xεσ2
6( ) >
+
+ P sup ( ) ( )
n l t T
W t W n l x
ε
ε ε ε
ε
σ ε σ
≤ ≤
− >
2 2
6 ≤
≤ P sup ( )
0
2
6
1 ≤ ≤=
>
∑
τ ε
ε
ε
τσ
lk
n
W x + P sup ( )
[ / ]0
2
6
≤ ≤ −
>
τ ε ε
ε
ε
τσ
T nl
W x ≤
≤ n W x
l
P sup ( )
0
2
6
≤ ≤
>
τ ε
ε
ε
τσ + P sup ( )
0
2
6
≤ ≤
>
τ ε
ε
ε
τσ
l
W x ≤
≤
T
l
W x
lε
τσ
ε τ ε
ε
ε
+
>
≤ ≤
1
0
2
6P sup ( ) ≤
≤
T
l
W x
lε
τ σ
ε τ ε
ε
ε
+
>
≤ ≤
1
0
6
2P sup ( )� / ≤
≤ 4 1 6
2T
l
W l x
ε
ε σ
ε
ε ε+
>{ }P � ( ) / ≤
≤ 4 1 1 6
2T
l
P W x l
ε
σ ε
ε
ε ε+
>{ }� ( ) / ≤ 8 1
2
6
2
2
T
l
x
KD lε εε ψ ε
+
−
exp . (40)
Obæedynqq ocenky (27), (29), (38) – (40), poluçaem ocenku
P sup ( ) ( )
0
6 5 3 4
≤ ≤
− > + + +
t T
W t t x x x xσ ςε ε� +
+
T
l
ce x
Kch
ε
ε
γε
γ ε+
+ +−1 12 2
4
1 ≤ 8 1
2
6
2
2
T
l
x
KD lε εε ψ ε
+
−
exp +
+ 8
2
5
2
2exp −
( )
x
TKD h lψ ε ε/
+
T
l
ce h
ε ε
γ ε+
−1 12 +
+ 4
2
4
2 2
2
2exp −
x b
TD
εσ
+ 4 1
2
1
2
2
T
l
x
l KDε εε ε ψ
+
−
exp +
+ exp
/
−
+ +
x
K b
T
l
3
1 2
256
1
1
2 2
1
ε εε ε
.
V¥byraq xi = εδ , 0 < δ < 1 4/ , i = 1, … , 5, lε = 1/ ε , hε = 1 1 4/ε δ/ −
, ymeem
P sup ˜ ( ) ( ) / /
0
6 1 12
41 4
≤ ≤
−− > + +
+
−
t T
W t t
T
ce
Kcσ ς ε ε
ε
ε
γε ε
δ γ ε δ
≤
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
750 B. V. BONDAREV, S. M. KOZÁR|
≤ 8 1
1
2 2 1 2 2
T
KDε εψ
δ+
−
−exp
/
+ 8
1
2 2 1 4
exp
/
−
−TKDψ
δε
+
+
T
l
ce
ε ε
γ ε δ
+
− −
1 12
1 4/ /
+ 4
2
2
1 2 2
2
2
exp
/
−
−
σ
ε δ TD
+
+ 4 1
1
21 2 2 2
T
KDε ε δ
ψ
+
−
−exp
/
+
+ exp
/
/
−
+ +
−
1
256
1
1
2 2
1
1 2
1 2
K
T
ε εδ .
Yz posledneho s uçetom (21) ymeem (20).
TeoremaF2 dokazana.
Sledstvye 1. V uslovyqx teorem¥ 2 spravedlyv¥ ocenky
P sup ( ) ( ) ( ) ( )
/
0 0≤ ≤
( ) ( ) + >∫
t T
t
s s dW s W tε ψ ξ β ξ σ
ε
ε� δδ ε
γε +
4 cK
≤ γ ε .
Sledstvye 2. Spravedlyva ocenka
M sup ( ) ( )
0
2
≤ ≤
+
t T
m
t W tς σε ε� ≤ max , ( , )δ γε ε
2
0
m D m T( ) , (41)
hde
D m T0( , ) = 1 + 4
4
4 1
2 12
2
m m m
m
mD K
m
m
T mψ
/ ( )!!
−
− +
+ 16
2 4
4 1
2 4 1
2
2
2
m
m
m
m
cK
T
m
m
m m
γ
+
−
−
( )
m
m mD Kψ
2 .
Dejstvytel\no, tak kak yz ocenky (20) sleduet ocenka
M sup ( ) ( )
0
2
≤ ≤
+
t T
m
t W tς σε ε� ≤ δε
2m + γ ς σε ε εM sup ( ) ( )
/
0
4
1 2
≤ ≤
+
t T
m
t W t� ≤
≤ δε
2m + 4
0
4 2
0
m
t T
m m
t T
t Wγ ς σε ε εM Msup ( ) sup (
≤ ≤ ≤ ≤
+ � tt
m
)
/
4
1 2
≤
≤ δε
2m + 4
4
4 10
4
1 2
m
t T
m mt
m
m
γ ς σε εM sup ( )
/
≤ ≤
+
−
−
2
2 1
m
mT m( )!!
(42)
y v sylu toho, çto v dannom sluçae spravedlyva ocenka
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
PEREMEÍYVANYE „PO YBRAHYMOVU”. OCENKA SKOROSTY SBLYÛENYQ … 751
M sup ( ) ( ) ( )
/
0 0
4
≤ ≤
( ) ( )∫
τ
τ ε
ε ψ ξ β ξ
T
m
s s dW s ≤
≤ T
m
m
m m D Km
m m
m m2
4 2
4 24
4 1
2 4 1
−
−
( ) ψ (43)
(v spravedlyvosty (43) netrudno ubedyt\sq, vospol\zovavßys\ ocenkoj dlq mo-
mentov supremuma neprer¥vnoho martynhala [19, s. 174]), yspol\zuq sootno-
ßenye
sup ( )
0≤ ≤t T
tςε ≤ ε
γ
2 cK
+ sup ( )
0≤ ≤t T
tηε ,
s uçetom (43) ymeem
sup ( )
0
4
≤ ≤t T
mtςε ≤ ε
γ
2 4 1
4
2
2m m
m
cK−
+ 24 1
0
4m
t T
mt−
≤ ≤
sup ( )ηε ≤
≤ ε
γ
2 4 1
4
2
2m m
m
cK−
+ 2
4
4 1
2 4 14 1 2
4 2
4m m
m m
mT
m
m
m m D K−
−
−
( ) ψ
22m .
(44)
Yz (42) s uçetom (44) poluçaem (41).
Sledstvye 3. Spravedlyva ocenka
M sup ( ) ( )
0
2
≤ ≤
+
t T
m
t W tη σε ε� ≤ δ ε
γε +
6
2
cK
m
+
+ γ η σε ε εM sup ( ) ( )
/
0
4
1 2
≤ ≤
+
t T
m
t W t� ≤ δ ε
γε +
6
2
cK
m
+
+ 4
0
4 4
0
4m
t T
m m
t T
m
t W tγ η σε ε εM Msup ( ) sup ( )
≤ ≤ ≤ ≤
+
�
1 2/
≤
≤ δ ε
γε +
6
2
cK
m
+
+F 4
4
4 1
2 4 12
2 2
4 2m m
m m
mT
m
m
m m D Kγ ε ψ−
−
( ) mm
+
+F σ4
4
2
1 2
4
4 1
4 1m
m
mm
m
T m
−
−
( )!!
/
≤ δ ε
γε +
4
2
cK
m
+
+F 4
4
4 1
2 2 1 4 1m m
m
mT
m
m
m m m
−
−( ) + − γ ε ( ) ( )!! DD Km m
ψ
2 ≤
≤ max , ( , , )δ ε
γ
γε ε+
4
2
1
cK
D m T K
m
,
hde
ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
752 B. V. BONDAREV, S. M. KOZÁR|
D m T K1( , , ) = 1 +
+ 4
4
4 1
2 2 1 4 1m m
m
mT
m
m
m m m D
−
−( ) + − ( ) ( )!! ψ
22m mK .
V zaklgçenye pryvedem nekotor¥e prymer¥.
Prymer 1. Pust\ α( )x = sin2 1
2
πx − , β( )x = 1, f x( ) = cos2 πx , tohda
ϑ
π
π( ) exp sinx x= { }1
2
2 , ϑ( )1 1= ,
G x0( ) = exp sin exp sin−
∫
1
2
2
1
2
2
0
1
π
π
π
πx x dx ,
ρ( )x = exp sin exp sin−
−
∫
1
2
2
1
2
2
0
1
π
π
π
πx x dx
−1
,
f = 1 + 1
1
2
21 2
0
1
−( ) −
−
−
∫e x dx/ exp sinπ
π
π
11
.
Prymer 2. Pust\ α( )x = −1 , β( )x = 1, f x( ) = 2 2cos πx , tohda ϑ( )x =
= e x2 , ϑ( )1 2= e ,
G x
e
e
0
2
2
1
1
( ) =
−
+
, ρ( )x ≡ 1 , f = 1.
Prymer 3. Pust\ α( )x = 0 , β( )x = 1, f x( ) = 2 2cos πx , tohda ϑ( )x ≡ 1 ,
G x0( ) ≡ 1, ρ( )x ≡ 1 , f = 1.
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– 45. – S.F159 – 251.
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V¥p. 2. – S. 225 – 238.
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Visn. Kyiv. un-tu. Fiz-mat. nauky. – 2001. – Vyp.F4. – S. 104 – 113.
4. Utev S. A. Neravenstva dlq summ slabozavysym¥x sluçajn¥x velyçyn y ocenky skorosty
sxodymosty v pryncype ynvaryantnosty //Trud¥ Yn-ta matematyky SO AN SSSR. – 1984. –
3. – S. 50 – 77.
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| id | umjimathkievua-article-2905 |
| institution | Ukrains’kyi Matematychnyi Zhurnal |
| keywords_txt_mv | keywords |
| language | rus English |
| last_indexed | 2026-03-24T02:32:33Z |
| publishDate | 2010 |
| publisher | Institute of Mathematics, NAS of Ukraine |
| record_format | ojs |
| resource_txt_mv | umjimathkievua/b9/2c8df8e3fada3775f3db2a3fae7f2bb9.pdf |
| spelling | umjimathkievua-article-29052020-03-18T19:40:12Z Mixing “In the sense of Ibragimov.” Estimate for the rate of approach of a family of integral functionals of a solution of a differential equation with periodic coefficients to a family of wiener processes. Some applications. I Перемешивание „по Ибрагимову". Оценка скорости сближения семейства интегральных функционалов от решения дифференциального уравнения с периодическими коэффициентами с семейством вииеровских процессов. Некоторые приложения. I Bondarev, B. V. Kozyr', S. M. Бондарев, Б. В. Козырь, С. М. Бондарев, Б. В. Козырь, С. М. We prove that a bounded 1-periodic function of a solution of a time-homogeneous diffusion equation with 1-periodic coefficients forms a process that satisfies the condition of uniform strong mixing. We obtain an estimate for the rate of approach of a certain normalized integral functional of a solution of an ordinary time-homogeneous stochastic differential equation with 1-periodic coefficients to a family of Wiener processes in probability in the metric of space $C[0, T]$. As an example, we consider an ordinary differential equation perturbed by a rapidly oscillating centered process that is a 1-periodic function of a solution of a time-homogeneous stochastic differential equation with 1-periodic coefficients. We obtain an estimate for the rate of approach of a solution of this equation to a solution of the corresponding Itô stochastic equation. Доведено, що обмежена 1-періодична функція від розв'язку однорідного за часом дифузійного рівняння з 1-періодичними коефіцієнтами утворює процес, що задовольняє умову рівномірного сильного перемішування. Встановлено оцінку швидкості зближення за ймовірністю в метриці простору $C[0, T]$ деякого нормованого інтегрального функціонала від розв'язку звичайного однорідного за часом стохастичного диференціального рівняння з 1-періодичними коефіцієнтами з сім'єю віперових процесів. Як приклад, розглянуто звичайне диференціальне рівняння, збурене швидкоосцилюючим центрованим процесом, який є 1-періодичною функцією від розв'язку однорідного за часом стохастичного диференціального рівняння з 1-періодичними коефіцієнтами. Встановлено оцінку швидкості зближення розв'язку такого рівняння з розв'язком відповідного стохастичного рівняння Іто. Institute of Mathematics, NAS of Ukraine 2010-06-25 Article Article application/pdf https://umj.imath.kiev.ua/index.php/umj/article/view/2905 Ukrains’kyi Matematychnyi Zhurnal; Vol. 62 No. 6 (2010); 733–753 Український математичний журнал; Том 62 № 6 (2010); 733–753 1027-3190 rus en https://umj.imath.kiev.ua/index.php/umj/article/view/2905/2561 https://umj.imath.kiev.ua/index.php/umj/article/view/2905/2562 Copyright (c) 2010 Bondarev B. V.; Kozyr' S. M. |
| spellingShingle | Bondarev, B. V. Kozyr', S. M. Бондарев, Б. В. Козырь, С. М. Бондарев, Б. В. Козырь, С. М. Mixing “In the sense of Ibragimov.” Estimate for the rate of approach of a family of integral functionals of a solution of a differential equation with periodic coefficients to a family of wiener processes. Some applications. I |
| title | Mixing “In the sense of Ibragimov.” Estimate for the rate of approach of a family of integral functionals of a solution of a differential equation with periodic coefficients to a family of wiener processes. Some applications. I |
| title_alt | Перемешивание „по Ибрагимову". Оценка скорости сближения семейства интегральных функционалов от решения дифференциального уравнения с периодическими коэффициентами с семейством вииеровских процессов. Некоторые приложения. I |
| title_full | Mixing “In the sense of Ibragimov.” Estimate for the rate of approach of a family of integral functionals of a solution of a differential equation with periodic coefficients to a family of wiener processes. Some applications. I |
| title_fullStr | Mixing “In the sense of Ibragimov.” Estimate for the rate of approach of a family of integral functionals of a solution of a differential equation with periodic coefficients to a family of wiener processes. Some applications. I |
| title_full_unstemmed | Mixing “In the sense of Ibragimov.” Estimate for the rate of approach of a family of integral functionals of a solution of a differential equation with periodic coefficients to a family of wiener processes. Some applications. I |
| title_short | Mixing “In the sense of Ibragimov.” Estimate for the rate of approach of a family of integral functionals of a solution of a differential equation with periodic coefficients to a family of wiener processes. Some applications. I |
| title_sort | mixing “in the sense of ibragimov.” estimate for the rate of approach of a family of integral functionals of a solution of a differential equation with periodic coefficients to a family of wiener processes. some applications. i |
| url | https://umj.imath.kiev.ua/index.php/umj/article/view/2905 |
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