On the ergodic theorem in the Kozlov–Treshchev form for an operator semigroup

We study nonuniform ergodic averages of the Kozlov – Treshchev type for operator semigroups and obtain estimates for the corresponding maximal functions.

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Бібліографічні деталі
Дата:2010
Автори: Korolev, A. V., Королев, А. В.
Формат: Стаття
Мова:Російська
Англійська
Опубліковано: Institute of Mathematics, NAS of Ukraine 2010
Онлайн доступ:https://umj.imath.kiev.ua/index.php/umj/article/view/2901
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Назва журналу:Ukrains’kyi Matematychnyi Zhurnal
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Ukrains’kyi Matematychnyi Zhurnal
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author Korolev, A. V.
Королев, А. В.
Королев, А. В.
author_facet Korolev, A. V.
Королев, А. В.
Королев, А. В.
author_sort Korolev, A. V.
baseUrl_str https://umj.imath.kiev.ua/index.php/umj/oai
collection OJS
datestamp_date 2020-03-18T19:39:51Z
description We study nonuniform ergodic averages of the Kozlov – Treshchev type for operator semigroups and obtain estimates for the corresponding maximal functions.
first_indexed 2026-03-24T02:32:27Z
format Article
fulltext UDK 519.21 A. V. Korolev (Mosk. un-t ym. M. V. Lomonosova, Rossyq) OB ∏RHODYÇESKOJ TEOREME V FORME KOZLOVA – TREWEVA DLQ POLUHRUPPÁ OPERATOROV * We study nonuniform ergodic averagings of the Kozlov – Treshchev type for operator semigroups. We obtain estimates for the corresponding maximal functions. Vyvçagt\sq nerivnomirni erhodyçni userednennq typu Kozlova – Treweva dlq operatornyx piv- hrup. Otrymano ocinky dlq vidpovidnyx maksymal\nyx funkcij. V rabotax [1, 2] naçato rassmotrenye neravnomern¥x usrednenyj obweho vyda F f x f T x dst t s( ) ( ) ( )= ∞ ∫ ν 0 dlq polupotokov Tt{ } s ynvaryantnoj meroj µ . Dlq absolgtno neprer¥vn¥x veroqtnostn¥x mer ν na poluosy y ohranyçenn¥x funkcyj f b¥lo dokazano, çto pry t → + ∞ velyçyn¥ F f xt ( ) pry µ-poçty vsex x ymegt tot Ωe predel, çto y v sluçae klassyçeskoho ravnomernoho usrednenyq v teoreme Byrkhofa – Xynçyna. ∏to yssledovanye b¥lo prodolΩeno v rabote [3] (sm. takΩe [ 4 ], hl.610), hde b¥lo v¥qsneno, çto dlq neohranyçenn¥x funkcyj f πto utverΩde- nye terqet sylu, odnako pry nekotor¥x sootnoßenyqx meΩdu xarakteramy yn- tehryruemosty f y plotnosty mer¥ ν ymegtsq poloΩytel\n¥e rezul\tat¥. V dannoj rabote prodolΩaetsq yssledovanye srednyx F f xt ( ) . V çastnosty, oka- z¥vaetsq, çto dlq sxodymosty ukazann¥x srednyx v Lp na okruΩnosty s meroj Lebeha moΩno otkazat\sq ot absolgtnoj neprer¥vnosty mer¥ ν. Krome toho, nekotor¥e rezul\tat¥, poluçenn¥e v [3], obobwagtsq na operatorn¥j sluçaj, kohda poluhruppa dejstvuet v L1( )µ . Teorema 1. Pust\ ( , )X λ — proyzvedenye n okruΩnostej s normyrovan- noj meroj Lebeha, a Ts s, ,…{ } — n-parametryçeskaq poluhruppa sdvyhov na X, t.6e. Ts s, ,… x : = ( , , )T x T xs s n1 … , hde Ts — povorot i-j okruΩnosty na uhol −si . Pust\ ν — proyzvol\naq veroqtnostnaq mera na R+ n , ymegwaq preobrazovanye Fur\e ν̂ . Ravenstvo lim ( ) ( ) ( ) ( min ( , , ) , , t t ts tsf T x d s f x d … → +∞ …( ) −ν λ xx X L p ) ( ) ∫∫ = R λ 0 (1) v¥polneno dlq lgboj funkcyy f Lp∈ ( )λ pry p ∈ +∞[ ]1, v toçnosty tohda, kohda pry t → +∞ v¥polneno sootnoßenye ˆ( )ν t → 0. Dokazatel\stvo. PredpoloΩym, çto ˆ( )ν t → 0 pry t → +∞ . Polo- Ωym Tts : = Tts ts, ,… pry t = ( , , )t tn1 … y s = ( , , )s sn1 … . Tohda dlq lgboj funkcyy g C X∈ ( ) dlq kaΩdoho x X∈ v¥polneno ravenstvo lim ( ) ( ) min ( , , )t t tsg T x ds … → +∞ ( )∫ ν R = g x dx X ( ) ( )λ∫ . * V¥polnena pry podderΩke Rossyjskoho fonda fundamental\n¥x yssledovanyj (proekt¥ 07- 01-00536, 08-01-90431-Ukr.). © A. V. KOROLEV, 2010 702 ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 5 OB ∏RHODYÇESKOJ TEOREME V FORME KOZLOVA – TREWEVA … 703 Yz teorem¥ Lebeha sleduet, çto πtot predel suwestvuet y v Lp ( )λ . Pust\ te- per\ f Lp∈ ( )λ . Voz\mem posledovatel\nost\ neprer¥vn¥x funkcyj gk na X takyx, çto f gk L− ( )λ → 0 pry k → + ∞. Pust\ ε > 0. V¥berem takoe N > 0, çto pry vsex k > N v¥polneno neravenstvo f gk L− ( )λ < ε. Najdetsq t0 0≥ takoe, çto ukazannaq v (1) norma v¥raΩenyq dlq gk vmesto f budet men\ße ε pry vsex t = ( , , )t tn1 … , dlq kotor¥x t ti > 0 , i = 1, … , n. Tohda dlq takyx k, t ymeem f T x d s f x dx ts X L p ( ) ( ) ( ) ( ) ( ) ( ) − ∫∫ ν λ λR ≤ ( ) ( ) ( ) ( ) f g T x d sk ts L p − ( )∫ ν λR + + g T x d s g x dxk ts k X L p ( ) ( ) ( ) ( ) ( ) ( ) − ∫∫ ν λ λR + g x f x dxk X L p ( ) ( ) ( ) ( ) −( )∫ λ λ ≤ 3ε, tak kak ( ) ( ) ( ) ( ) f g T x d sk ts L p − ( )∫ ν λR ≤ ( ) ( ) ( ) ( )f g T x dx dsk ts p X − ( )∫∫ λ ν R = = f x g x dx dsk p X ( ) ( ) ( ) ( )−∫∫ λ ν R ≤ ε. PredpoloΩym teper\, çto ˆ( )ν t ne stremytsq k 0 pry t → +∞ . Tohda dlq funkcyy f x xn( , , )1 … : = exp (ix1 + … + ixn ) ymeem f T x d s f x dx ts X L p ( ) ( ) ( ) ( ) ( ) ( ) − ∫∫ ν λ λR = ˆ ( )ν t p , no poslednee v¥raΩenye ne stremytsq k 0 pry min ( , , )t tn1 … → + ∞. Teorema dokazana. Pust\ ( , )X λ — edynyçnaq okruΩnost\ s meroj Lebeha, Tt — povorot ok- ruΩnosty na uhol −t . Yzvestno, çto suwestvuet takaq bezatomyçeskaq synhu- lqrnaq borelevskaq veroqtnostnaq mera ν na 0 1,[ ] , çto ee preobrazovanye Fur\e ν̂ stremytsq k nulg na beskoneçnosty (sm. [5, s. 35]). Tohda dlq lgboj funkcyy f Lp∈ ( )λ srednye F f xt ( ) sxodqtsq v Lp ( )λ . Odnako ostaetsq ot- kr¥t¥m vopros o suwestvovanyy synhulqrn¥x mer, dlq kotor¥x ymeetsq sxody- most\ srednyx poçty vsgdu. Rassmotrym teper\ bolee obwug sytuacyg, kohda Tt{ } — poluhruppa polo- Ωytel\n¥x operatorov na L1( )µ , hde µ — veroqtnostnaq mera na yzmerymom prostranstve ( , )X A . Sluçaj klassyçeskyx ravnomern¥x usrednenyj b¥l ras- smotren v [6, 7]. Pust\ Tt{ } — syl\no yzmerymaq poluhruppa. V stat\e [7] po- kazano, çto yz uslovyj Tt 1 ≤ 1 y Tt ∞ ≤ 1 sleduet neravenstvo T f x s dss ( ) ( ) ( )β 0 ∞ ∫ ≤ f x s ds∗ ∞ ∫( ) ( )β 0 , hde ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 5 704 A. V. KOROLEV f x t T f x ds t s t ∗ = ∫( ) : sup ( ) ( ) 1 0 dlq lgboj funkcyy f Lp∈ ( )µ y lgboj poloΩytel\noj y nevozrastagwej funkcyy β na R+ . Zameçanye 1. Pust\ ν = ρ ds — veroqtnostnaq mera na 0, +∞[ ) , pryçem suwestvuet takaq nevozrastagwaq funkcyq β ∈ L1( , )R+ λ , çto ρ ≤ β na 0, +∞[ ) . Tohda ( ) ( ) ( )T f x s dsts ρ 0 ∞ ∫ ≤ f x s ds∗ ∞ ∫( ) ( )β 0 . Esly p > 1, to suwestvuet postoqnnaq C, ne zavysqwaq ot f, takaq, çto sup ( ) ( ) ( ) ( ) t s L T f x s ds p β µ0 ∞ ∫ ≤ C f L p( )µ . Çtob¥ proveryt\ pervoe neravenstvo, dostatoçno v¥polnyt\ zamenu u : = t s. Vtoroe neravenstvo neposredstvenno sleduet yz teorem¥ ob ocenke norm¥ f ∗ (sm. [6, s. 735], teorema 7). Sledugwee utverΩdenye rasprostranqet ocenku, poluçennug v [6, s. 735] (teorema 7), na sluçaj usrednenyj s plotnost\g. Teorema 2. Pust\ Tt — syl\no yzmerymaq poluhruppa poloΩytel\n¥x ope- ratorov na L1( )µ , pryçem Tt 1 ≤ 1 y Tt ∞ ≤ 1. Pust\ ρ λ∈ Lq ( ) , hde λ — mera Lebeha na R+ , ρ ≥ 0 y suwestvuet nevozrastagwaq funkcyq β ∈ ∈ L1( , )R+ λ takaq, çto dlq nekotoroho t0 0≥ ymeem ρ( )s ≤ β( )s pry s ∈ ∈ t0, +∞[ ) . Tohda dlq lgboj funkcyy f Lp∈ ( )µ , p−1 + q−1 < 1, p, q ∈ 1, +∞( ] , v¥polneno neravenstvo sup ( ) ( ) ( ) t ts L T f x s ds p ( ) +∞ ∫ ρ µ0 ≤ C p t fq q L t L Lq p( ) ( ) , , ( ) ( )0 1 0 −  ( ) +   ρ βλ λ µ , hde C p( ) : = 2 1 1 p p p −     / . Dokazatel\stvo. Sluçaj p = + ∞ sleduet yz neravenstva T ∞ ≤ 1. Pust\ p < + ∞. Najdetsq ε > 0 takoe, çto ( )p − −ε 1 + q−1 = 1. PoloΩym σ : = : = ρI t0,[ ] y τ : = ρI t , +∞[ ) . Tohda v¥polneno neravenstvo sup ( ) ( ) ( ) t ts L T f x s ds p ( ) +∞ ∫ ρ µ0 ≤ sup ( ) ( ) ( ) t ts L T f x s ds p ( ) +∞ ∫ σ µ0 + + sup ( ) ( ) ( ) t ts L T f x s ds p ( ) +∞ ∫ τ µ0 . ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 5 OB ∏RHODYÇESKOJ TEOREME V FORME KOZLOVA – TREWEVA … 705 Snaçala ocenym pervoe slahaemoe. Po uslovyg Tt 1 ≤ 1 y Tt ∞ ≤ 1, otkuda pry kaΩdom t ymeem T f x T f xt p t p( ) ( )− −≤ε ε dlq µ-poçty vsex x . Yz teorem¥ Fubyny sleduet, çto dlq µ-poçty vsex x su- westvugt takye mnoΩestva Bx ⊂ +R , çto λ( \ )R+ Bx = 0 y pry t Bx∈ v¥pol- neno ukazannoe neravenstvo. Poluçaem T f x s dsts ( ) ( )σ 0 +∞ ∫ ≤ σ λ ε ε L ts p t p q T f x ds ( ) ( ) ( ) − − ∫       − 0 1 ≤ ≤ σ λ ε ε L s p t p q t T f x ds ( ) ( ) ( ) 1 0 1 − − ∫       − ≤ ≤ t t t T f x dsq q L s p t p q0 1 0 0 1( ) ( ) ( ( )− − − ∫       σ λ ε εε)−1 dlq µ-poçty vsex x X∈ , pryçem suwestvovanye yntehralov v prav¥x çastqx neravenstv sleduet yz πrhodyçeskoj teorem¥, prymenennoj k poslednemu ynteh- ralu. Tohda sup ( ) ( ) t tsT f x s dsσ 0 +∞ ∫ ≤ t t T f x dsq q L t s p t q0 1 0 1( ) ( ) ( sup ( )− −∫       σ λ ε pp − ε) dlq µ-poçty vsex x X∈ . Poskol\ku f Lp∈ ( )µ , to f p − ε ∈ Lp p/( )( )− ε µ y, sohlasno teoreme 7 [6, s. 735], v¥polneno neravenstvo sup ( ) ( ) ( ) ( ) t s p t p L t T f x ds p 1 0 1 − − ∫       − ε ε µ ≤ C p f p L p p p ( ) ( ) ( ) ( ) / ( ) − − − − ε µ ε ε 1 = C p f Lp( ) ( )µ . Prymenqq poslednee neravenstvo k ocenkam, poluçenn¥m v¥ße, okonçatel\no poluçaem sup ( ) ( ) ( ) t ts L T f x s ds p σ µ0 +∞ ∫ ≤ ≤ t t T f x dsq q L t s p t q0 1 0 1( ) ( ) ( sup ( )− −∫       σ λ ε pp L p − −ε µ ) ( ) 1 ≤ ≤ t C p fq q L Lq p0 1( ) ( ) ( ) ( )− σ λ µ . Teper\ ocenym yntehral s plotnost\g τ. MoΩno sçytat\, çto β ≥ 0. Ymeem T f x s dsts ( ) ( )τ 0 +∞ ∫ ≤ T f x s dsts ( ) ( )β 0 +∞ ∫ ≤ ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 5 706 A. V. KOROLEV ≤ β µL t s t t T f x ds1 1 0 ( ) sup ( )∫ dlq µ-poçty vsex x X∈ , çto sleduet yz zameçanyq 1. Snova prymenqq teoremu yz [6, s. 735], naxodym sup ( ) ( ) ( ) t ts L T f x s ds p τ µ0 +∞ ∫ ≤ C p f L L p( ) ( ) ( ) β λ µ1 . Okonçatel\no sup ( ) ( ) ( ) t ts L T f x s ds p ( ) +∞ ∫ ρ µ0 ≤ C p f t L q q L t Lp q( ) ( ) ( ) , , ( )µ λ λρ β0 1 0 1 −  ( ) +    . Teorema dokazana. Rassmotrym sxodymost\ srednyx Ft dlq operatornoho sluçaq. Teorema 3. Pust\ Tt — syl\no yzmerymaq poluhruppa poloΩytel\n¥x ope- ratorov na L1( )µ , pryçem T 1 ≤ 1 y T ∞ ≤ 1. Pust\ f Lp∈ ( )µ y ρ ∈ ∈ Lq ( )λ — veroqtnostnaq plotnost\, hde λ — mera Lebeha na R+ , p−1 + + q−1 = 1 y p, q ∈ +∞[ ]1, . PredpoloΩym, çto v¥polneno odno yz uslovyj: i) plotnost\ ρ ymeet ohranyçenn¥j nosytel\ v otrezke a b,[ ] ; ii) p > 1 y suwestvuet nevozrastagwaq funkcyq β na 0, +∞[ ) , dlq ko- toroj β ≥ 0, β ∈6 Lq 0, +∞[ ) y ρ( )t ≤ β( )t na t0, ∞[ ) dlq nekotoroho t0 . Tohda dlq µ-poçty vsex x X∈ v¥polneno ravenstvo lim ( ) ( ) t tsT f x s ds → +∞ +∞ ∫ ρ 0 = ET f x( ) , (2) hde ET f — uslovnoe matematyçeskoe oΩydanye f otnosytel\no T — σ - alhebr¥ Tt -ynvaryantn¥x mnoΩestv. Dokazatel\stvo. MoΩno sçytat\, çto f ≥ 0. Pust\ nosytel\ ρ leΩyt v a b,[ ] . PoloΩym fN = min ( , )f N , gN = f – fN . Dlq ohranyçenn¥x funkcyj fN dokaz¥vaemoe utverΩdenye verno, poπtomu dlq µ-poçty vsex x pry vsex N spravedlyvo ravenstvo (2) dlq fN vmesto f. Pust\ t ≥ 0 y h st x N, , ( ) = = T g xts N ( )( ) . Po neravenstvu Hel\dera T g x s dsts N a b ( ) ( )( )∫ ρ ≤ ht x N L Lp q, , ( ) ( )λ λρ . V sylu µ-yntehryruemosty funkcyy x � T g xts N p( )( ) yz πrhodyçeskoj teore- m¥ sleduet, çto lim ( ) t ts N p a b T g x ds → ∞ ( )∫ = ( ) ( )b a g xN p− ET ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 5 OB ∏RHODYÇESKOJ TEOREME V FORME KOZLOVA – TREWEVA … 707 dlq µ-poçty vsex x . Pust\ ε > 0 fyksyrovano. Poskol\ku µ-poçty vsgdu v¥- polneno ravenstvo lim ( ) N N pg x → ∞ ET = 0, suwestvugt N0 y E ∈A s µ( )E > > 1 – ε takye, çto pry N > N0 spravedlyva ocenka ( ) ( )b a g xN p− ET < ε, x E∈ . Dlq µ-poçty lgboho x E∈ suwestvuet takoe çyslo T x( , )ε , çto pry vsex t ≥ ≥ T x( , )ε y N > N0 v¥polnen¥ neravenstva T g x dsts N p a b ( )( ) ≤∫ ε , T f x s ds f xts N a b N( ) ( ) ( )( ) − <∫ ρ εET . Yz neravenstv Tt 1 ≤ 1 y Tt ∞ ≤ 1 sleduet, çto dlq µ-poçty vsex x X∈ pry vsex t ≥ 0 ymeet mesto neravenstvo T f x dsts p a b ( )∫ ≤ T f x dsts p a b ( )∫ . Tohda dlq µ-poçty vsex x E∈ pry t ≥ T x( , )ε y N > N0 ymeem T g x s dsts N a b ( ) ( )( )∫ ρ ≤ ε ρ λLq ( ) . Okonçatel\no poluçaem T f x s ds f xts a b ( ) ( ) ( )( ) −∫ ρ ET < 2ε ε ρ λ+ Lq ( ) . Teper\ dostatoçno rassmotret\ sluçaj, kohda ρ — ohranyçennaq funkcyq y p > 1. MoΩno sçytat\, çto t0 0= . Ostalos\ prymenyt\ pred¥duwug teoremu y vospol\zovat\sq tem, çto dokaz¥vaemoe ravenstvo v¥polneno dlq vsex ohrany- çenn¥x yntehryruem¥x funkcyj f. 1. Kozlov V. V., Treshchev D. V. On new forms of the ergodic theorem // J. Dynam. Control Syst. – 2003. – 9, # 3. – P. 449 – 453. 2. Kozlov V. V., Trewev D. V. ∏volgcyq mer v fazovom prostranstve nelynejn¥x hamyl\tono- v¥x system // Teor. y mat. fyzyka. – 2003. – 136, # 3. – S. 496 – 506. 3. Bohaçev V. Y., Korolev A. V. Ob πrhodyçeskoj teoreme v forme Kozlova – Treweva // Dokl. RAN. – 2007. – 412, # 3. – S. 295 – 301. 5. Lukaç E. Xarakterystyçeskye funkcyy. – M.: Nauka, 1979. 6. Danford N., Ívarc DΩ. Lynejn¥e operator¥. I. Obwaq teoryq. – M.: Yzd-vo ynostr. lyt., 1962. 7. Dunford N., Schwartz J. T. Convergence almost everywhere of operator averages // J. Ration. Mech. and Anal. – 1956. – # 1. – P. 129 – 178. Poluçeno 30.11.09 ISSN 1027-3190. Ukr. mat. Ωurn., 2010, t. 62, # 5
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spelling umjimathkievua-article-29012020-03-18T19:39:51Z On the ergodic theorem in the Kozlov–Treshchev form for an operator semigroup Об эргодической теореме в форме Козлова - Трещева для полугруппы операторов Korolev, A. V. Королев, А. В. Королев, А. В. We study nonuniform ergodic averages of the Kozlov – Treshchev type for operator semigroups and obtain estimates for the corresponding maximal functions. Вивчаються нерівномірні ергодичні усереднення типу Козлова - Трещева для операторних пів-груп. Отримано оцінки для відповідних максимальних функцій. Institute of Mathematics, NAS of Ukraine 2010-05-25 Article Article application/pdf https://umj.imath.kiev.ua/index.php/umj/article/view/2901 Ukrains’kyi Matematychnyi Zhurnal; Vol. 62 No. 5 (2010); 702–707 Український математичний журнал; Том 62 № 5 (2010); 702–707 1027-3190 rus en https://umj.imath.kiev.ua/index.php/umj/article/view/2901/2553 https://umj.imath.kiev.ua/index.php/umj/article/view/2901/2554 Copyright (c) 2010 Korolev A. V.
spellingShingle Korolev, A. V.
Королев, А. В.
Королев, А. В.
On the ergodic theorem in the Kozlov–Treshchev form for an operator semigroup
title On the ergodic theorem in the Kozlov–Treshchev form for an operator semigroup
title_alt Об эргодической теореме в форме Козлова - Трещева для полугруппы операторов
title_full On the ergodic theorem in the Kozlov–Treshchev form for an operator semigroup
title_fullStr On the ergodic theorem in the Kozlov–Treshchev form for an operator semigroup
title_full_unstemmed On the ergodic theorem in the Kozlov–Treshchev form for an operator semigroup
title_short On the ergodic theorem in the Kozlov–Treshchev form for an operator semigroup
title_sort on the ergodic theorem in the kozlov–treshchev form for an operator semigroup
url https://umj.imath.kiev.ua/index.php/umj/article/view/2901
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