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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Datum:2010
Hauptverfasser: Bondarev, B. V., Kozyr', S. M., Бондарев, Б. В., Козырь, С. М.
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Sprache:Russisch
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Veröffentlicht: Institute of Mathematics, NAS of Ukraine 2010
Online Zugang:https://umj.imath.kiev.ua/index.php/umj/article/view/2905
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Назва журналу:Ukrains’kyi Matematychnyi Zhurnal
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Ukrains’kyi Matematychnyi Zhurnal
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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
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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. 1. Lypcer R. Í., Íyrqev A. N. Martynhal¥ y predel\n¥e teorem¥ dlq sluçajn¥x processov.// Ytohy nauky y texnyky. Sovr. probl. matematyky. Fundam. napravlenyq. – 1989. – 45. – S.F159 – 251. 2. Bondarev B. V. O neravenstve Kolmohorova – Haeka – Ren\y dlq normyrovann¥x yntehralov ot processov so slaboj zavysymost\g // Teoryq veroqtnostej y ee prymenenyq. – 1997. – V¥p. 2. – S. 225 – 238. 3. Bondar[v B. V., Zubko M. L. Pro ocinku ßvydkosti zbiΩnosti v pryncypi invariantnosti // 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. 5. Dav¥dov G. A. O sxodymosty raspredelenyj, poroΩdenn¥x stacyonarn¥my sluçajn¥my processamy // Teoryq veroqtnostej y ee prymenenyq. – 1968. – 13, # 4. – S. 730 – 737. 6. Çykyn D. O. Funkcyonal\naq predel\naq teorema dlq stacyonarn¥x processov: martyn- hal\n¥j podxod // Tam Ωe. – 1989. – 14, # 4. – S. 731 – 741. 7. Ûakod Û., Íyrqev A. N. Predel\n¥e teorem¥ dlq sluçajn¥x processov.: Per. s anhl. – M.: Fyzmatlyt, 1994. – T. 2. – 368 s. 8. Skoroxod A. V. Asymptotyçeskye metod¥ teoryy stoxastyçeskyx dyfferencyal\n¥x urav- nenyj. – Kyev: Nauk. dumka, 1987. – 328 s. 9. Bondarev Boris V., Zoobko Maxim L. The application of the invariance principle for stationary se- quences with mixing // Prykl. statystyka. Aktuarna ta finansova matematyka. – 2001. – # 1. – S. 49 – 59. 10. Bondarev B. V., Koz¥r\ S. M. Ob ocenke skorosty sblyΩenyq reßenyq ob¥knovennoho dyf- ferencyal\noho uravnenyq, vozmuwennoho fyzyçeskym bel¥m ßumom, y reßenyq soot- vetstvugweho uravnenyq Yto. I // Tam Ωe. – 2006. – # 2. – S. 63 – 91. ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6 PEREMEÍYVANYE „PO YBRAHYMOVU”. OCENKA SKOROSTY SBLYÛENYQ … 753 11. Bondarev B. V., Koz¥r\ S. M. Ob ocenke skorosty sblyΩenyq reßenyq ob¥knovennoho dyf- ferencyal\noho uravnenyq, vozmuwennoho fyzyçeskym bel¥m ßumom, y reßenyq soot- vetstvugweho uravnenyq Yto. 2 // Tam Ωe. – 2007. – #1. – S. 68 – 97. 12. Bondarev B. V., Kovtun E. E. Ocenka skorosty sblyΩenyq v ob¥knovenn¥x dyfferen- cyal\n¥x uravnenyqx, naxodqwyxsq pod vozdejstvyem sluçajn¥x processov s b¥str¥m vremenem // Ukr. mat Ωurn. – 2005. – 57, # 4. – S. 435 – 457. 13. Bondarev B. V., Kovtun E. E. Pryncyp ynvaryantnosty dlq stacyonarn¥x processov. Ocenka skorosty sxodymosty // Visn. Donec. un-tu. Ser. A. – 2004. – # 1. – S. 31 – 55. 14. Safonova O. A. Ob asymptotyçeskom povedenyy yntehral\n¥x funkcyonalov ot dyffu- zyonn¥x processov s peryodyçeskymy koπffycyentamy // Ukr. mat. Ωurn. – 1992. – 44, # 2. – S. 245 – 252. 15. Ûurbenko Y. H. Analyz stacyonarn¥x y odnorodn¥x sluçajn¥x system. – M.: Yzd-vo Mosk. un-ta, 1987. – 240 s. 16. Bensoussan A., Lions J.-L., Papanicolau G. Asymptotic analysis for periodic structures. – North- Holland Publ. Comp., 1978. – 700 p. 17. Ybrahymov Y. A., Lynnyk G. V. Nezavysym¥e y stacyonarno-svqzann¥e velyçyn¥. – M.: Nauka, 1965. – 524 s. 18. Hyxman Y. Y., Skoroxod A. V. Stoxastyçeskye dyfferencyal\n¥e uravnenyq. – Kyev: Nauk. dumka, 1968. – 354 s. 19. Hyxman Y. Y., Skoroxod A. V. Stoxastyçeskye dyfferencyal\n¥e uravnenyq y yx prylo- Ωenyq. – Kyev: Nauk. dumka, 1982. – 612 s. 20. Berkes I., Philipp W. Approximation theorem for independent and weakdependent random vektors // Ann. Probab. – 1979. – 1, # 1. – P. 29 – 54. 21. Saxanenko A. Y. Skorost\ sxodymosty v pryncype ynvaryantnosty dlq raznoraspredelen- n¥x velyçyn s πksponencyal\n¥my momentamy // Trud¥ Yn-ta matematyky SO AN SSSR. – 1984. – 3. – S. 4 – 49. 22. Saxanenko A. Y. Ocenky v pryncype ynvaryantnosty // Tam Ωe. – 1985. – 5. – S. 27 – 44. 23. Saxanenko A. Y. O toçnosty normal\noj approksymacyy v pryncype ynvaryantnosty // Tam Ωe. – 1989. – 13. – S. 40 – 66. 24. Bondarev B. V., Kolosov A. A. K voprosu o pryncype ynvaryantnosty dlq slabozavysym¥x sluçajn¥x velyçyn // Prykl. statystyka. Aktuarna ta finansova matematyka. – 2002. – # 2. – S. 63 – 71. 25. Petrov V. V. Summ¥ nezavysym¥x sluçajn¥x velyçyn. – M.: Nauka, 1972. – 414 s. 26. Kolosov A. A. O postroenyy vynerovskoho processa po koneçnoj posledovatel\nosty neza- vysym¥x haussovskyx velyçyn // Prykladna statystyka. Aktuarna ta finansova matematyka. – 2007. – # 1. – S. 97 – 101. Poluçeno 21.10.08, posle dorabotky — 01.04.10 ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 6
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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&quot;. Оценка скорости сближения семейства интегральных функционалов от решения дифференциального уравнения с периодическими коэффициентами с семейством вииеровских процессов. Некоторые приложения. I Bondarev, B. V. Kozyr&#039;, 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&#039;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&#039;язку звичайного однорідного за часом стохастичного диференціального рівняння з 1-періодичними коефіцієнтами з сім&#039;єю віперових процесів. Як приклад, розглянуто звичайне диференціальне рівняння, збурене швидкоосцилюючим центрованим процесом, який є 1-періодичною функцією від розв&#039;язку однорідного за часом стохастичного диференціального рівняння з 1-періодичними коефіцієнтами. Встановлено оцінку швидкості зближення розв&#039;язку такого рівняння з розв&#039;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&#039; S. M.
spellingShingle Bondarev, B. V.
Kozyr&#039;, 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&quot;. 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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