On the ergodicity of nonlinear Fokker–Planck flows in $L^{1}(\mathbb R^d)$

UDC 517.9 We prove that a nonlinear semigroup $S(t)$ in $L^1(\mathbb{R}^d),$ $d\ge 3,$ associated with the nonlinear Fokker–Planck equation $u_t-\Delta\beta(u)+{\rm div }(Db(u)u)=0,$ $u(0)=u_0,$ in $(0,\infty)\times\mathbb{R}^d,$ with suitable conditions imposed on the coefficients $\beta\colon \mat...

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Date:2026
Main Authors: Barbu, Viorel, Röckner, Michael
Format: Article
Language:English
Published: Institute of Mathematics, NAS of Ukraine 2026
Online Access:https://umj.imath.kiev.ua/index.php/umj/article/view/8286
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Journal Title:Ukrains’kyi Matematychnyi Zhurnal
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Ukrains’kyi Matematychnyi Zhurnal
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author Barbu, Viorel
Röckner, Michael
Barbu, Viorel
Röckner, Michael
author_facet Barbu, Viorel
Röckner, Michael
Barbu, Viorel
Röckner, Michael
author_sort Barbu, Viorel
baseUrl_str https://umj.imath.kiev.ua/index.php/umj/oai
collection OJS
datestamp_date 2026-03-21T13:30:45Z
description UDC 517.9 We prove that a nonlinear semigroup $S(t)$ in $L^1(\mathbb{R}^d),$ $d\ge 3,$ associated with the nonlinear Fokker–Planck equation $u_t-\Delta\beta(u)+{\rm div }(Db(u)u)=0,$ $u(0)=u_0,$ in $(0,\infty)\times\mathbb{R}^d,$ with suitable conditions imposed on the coefficients $\beta\colon \mathbb{R}\to\mathbb{R},$ $-D\colon \mathbb{R}^d\to\mathbb{R}^d,$ and $b\colon \mathbb{R}\to\mathbb{R},$ is mean ergodic. In particular, this implies the mean ergodicity of the time marginal laws for the solutions to the corresponding McKean–Vlasov stochastic differential equation. This completes the results established in [V. Barbu, M. Röckner, The invariance principle for nonlinear Fokker–Planck equations, J. Different. Equat., 315, 200–221 (2022)] on the nature of the corresponding omega-set $\omega(u_0)$ for $S(t)$ in the case where the flow $S(t)$ in $L^1(\mathbb{R}^d)$ does not have a fixed point and, hence, the corresponding stationary Fokker–Planck equation has no solutions.
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spelling umjimathkievua-article-82862026-03-21T13:30:45Z On the ergodicity of nonlinear Fokker–Planck flows in $L^{1}(\mathbb R^d)$ On the ergodicity of nonlinear Fokker–Planck flows in $L^{1}(\mathbb R^d)$ Barbu, Viorel Röckner, Michael Barbu, Viorel Röckner, Michael Fokker-Planck semigroup ergodic UDC 517.9 We prove that a nonlinear semigroup $S(t)$ in $L^1(\mathbb{R}^d),$ $d\ge 3,$ associated with the nonlinear Fokker–Planck equation $u_t-\Delta\beta(u)+{\rm div }(Db(u)u)=0,$ $u(0)=u_0,$ in $(0,\infty)\times\mathbb{R}^d,$ with suitable conditions imposed on the coefficients $\beta\colon \mathbb{R}\to\mathbb{R},$ $-D\colon \mathbb{R}^d\to\mathbb{R}^d,$ and $b\colon \mathbb{R}\to\mathbb{R},$ is mean ergodic. In particular, this implies the mean ergodicity of the time marginal laws for the solutions to the corresponding McKean–Vlasov stochastic differential equation. This completes the results established in [V. Barbu, M. Röckner, The invariance principle for nonlinear Fokker–Planck equations, J. Different. Equat., 315, 200–221 (2022)] on the nature of the corresponding omega-set $\omega(u_0)$ for $S(t)$ in the case where the flow $S(t)$ in $L^1(\mathbb{R}^d)$ does not have a fixed point and, hence, the corresponding stationary Fokker–Planck equation has no solutions. УДК 517.9 Ергодичність нелінійних потоків Фоккера–Планка в $L^{1}(\mathbb R^d)$ Доведено, що нелінійна напівгрупа $S(t)$ у $L^1(\mathbb{R}^d),$ $d\ge 3,$ пов'язана з нелінійним рівнянням Фоккера–Планка $u_t-\Delta\beta(u)+{\rm div }(Db(u)u)=0,$ $u(0)=u_0,$ у $(0,\infty)\times\mathbb{R}^d,$ за відповідних умов на коефіцієнти $\beta\colon \mathbb{R}\to\mathbb{R},$ $D\colon \mathbb{R}^d\to\mathbb{R}^d$ і $b\colon \mathbb{R}\to\mathbb{R}$ є середньою ергодичною. Зокрема, це означає середню ергодичність граничних за часом законів для розв'язків відповідного стохастичного диференціального рівняння Маккіна–Власова. Це доповнює результати, встановлені в роботі [V. Barbu, M. Röckner, The invariance principle for nonlinear Fokker–Planck equations, J. Different. Equat., 315, 200–221 (2022)], про природу відповідної омега-множини $\omega(u_0)$ для $S(t)$ у випадку, коли потік $S(t)$ у $L^1(\mathbb{R}^d)$ не має нерухомої точки, і тому відповідне стаціонарне рівняння Фоккера–Планка не має розв'язків. Institute of Mathematics, NAS of Ukraine 2026-03-21 Article Article https://umj.imath.kiev.ua/index.php/umj/article/view/8286 10.3842/umzh.v77i4.8286 Ukrains’kyi Matematychnyi Zhurnal; Vol. 77 No. 4 (2025); 279 Український математичний журнал; Том 77 № 4 (2025); 279 1027-3190 en https://umj.imath.kiev.ua/index.php/umj/article/view/8286/10441 Copyright (c) 2025 Viorel Barbu, Michael Röckner
spellingShingle Barbu, Viorel
Röckner, Michael
Barbu, Viorel
Röckner, Michael
On the ergodicity of nonlinear Fokker–Planck flows in $L^{1}(\mathbb R^d)$
title On the ergodicity of nonlinear Fokker–Planck flows in $L^{1}(\mathbb R^d)$
title_alt On the ergodicity of nonlinear Fokker–Planck flows in $L^{1}(\mathbb R^d)$
title_full On the ergodicity of nonlinear Fokker–Planck flows in $L^{1}(\mathbb R^d)$
title_fullStr On the ergodicity of nonlinear Fokker–Planck flows in $L^{1}(\mathbb R^d)$
title_full_unstemmed On the ergodicity of nonlinear Fokker–Planck flows in $L^{1}(\mathbb R^d)$
title_short On the ergodicity of nonlinear Fokker–Planck flows in $L^{1}(\mathbb R^d)$
title_sort on the ergodicity of nonlinear fokker–planck flows in $l^{1}(\mathbb r^d)$
topic_facet Fokker-Planck
semigroup
ergodic
url https://umj.imath.kiev.ua/index.php/umj/article/view/8286
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