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In this paper, we investigate the long term dynamical behaviour of stochastic Hopfield neural network models driven by white noise with time delay, where the nonlinear drift and diffusion terms are both locally Lipschitz continuous. We establish the global-in-time solvability of these systems with locally Lipschitz continuous nonlinear drift and diffusion terms by using mean square uniform estimates of solutions. Furthermore, we demonstrate that the mean random dynamical system generated by the solution operators possesses a unique weak pullback mean random attractor in the Hilbert space $ L^2(\tilde {\Omega }, \mathcal {F}_\iota ; l^2)\times L^2\left (\tilde {\Omega }, \mathcal {F}_{\iota }; L^2((-\varrho,0), l^2)\right) $ L 2 (Ω ~ , F ι ; l 2) × L 2 (Ω ~ , F ι ; L 2 ((− ϱ , 0) , l 2)) . [ABSTRACT FROM AUTHOR]

This paper is concerned with the invariant probability measures supported on pullback attractors for 3D globally modified Navier–Stokes equations with delay. We first construct a family of invariant probability measures as well as periodic invariant probability measures when the forcing term is periodic in time. We then present some general results on the limiting behaviors of invariant measures and periodic invariant measures for non-autonomous dynamical systems, and further apply these results to the 3D globally modified Navier–Stokes equations with delay. More precisely, we prove that any limit of a sequence of invariant measures (respectively, periodic invariant measures) of such equations must be an invariant measure (respectively, a periodic invariant measure) of the corresponding limiting equations as parameter N tends to some positive number or the delay parameter approaches to zero. [ABSTRACT FROM AUTHOR]

This work aims to investigate the well-posedness and the existence of ergodic invariant measures for a class of third-grade fluid equations in bounded domain D ⊂ R d , d = 2 , 3 , in the presence of a multiplicative noise. First, we show the existence of a martingale solution by coupling a stochastic compactness and monotonicity arguments. Then, we prove a stability result, which gives the pathwise uniqueness of the solution and therefore the existence of strong probabilistic solution. Secondly, we use the stability result to show that the associated semigroup is Feller and by using “Krylov-Bogoliubov Theorem,” we get the existence of an invariant probability measure. Finally, we show that all the invariant measures are concentrated on a compact subset of L 2 , which leads to the existence of an ergodic invariant measure. [ABSTRACT FROM AUTHOR]

This article is concerned with the limiting behavior of invariant measures for stochastic reaction–diffusion equations driven by nonlinear noise on unbounded thin domains. We first show the existence of invariant measures when the diffusion terms are globally Lipschitz continuous. The uniform estimates on the tails of solutions are employed to present the tightness of a family of probability distributions of solutions in order to overcome the non-compactness of usual Sobolev embeddings on unbounded domains. Then, we prove any limit of invariant measures of the equations defined on (n + 1) -dimensional unbounded thin domains must be an invariant measure of the limiting system as the thin domains collapse onto the space R n . [ABSTRACT FROM AUTHOR]

The paper below is a written version of the 17th Andrzej Lasota Lecture presented on January 12th, 2024 in Katowice. During the lecture we tried to show the impact of Andrzej Lasota’s results on the author’s research concerning various fields of mathematics, including chaos and ergodicity of dynamical systems, Markov operators and semigroups and partial differential equations.

This paper deals with the long-term behavior of the solution to the nonlinear stochastic heat equation ∂ u ∂ t - 1 2 Δ u = b (u) W ˙ , where b is assumed to be a globally Lipschitz continuous function and the noise W ˙ is a centered and spatially homogeneous Gaussian noise that is white in time. We identify a set of nearly optimal conditions on the initial data, the correlation measure of the noise, and the weight function ρ , which together guarantee the existence of an invariant measure in the weighted space L ρ 2 (R d) . In particular, our result covers the parabolic Anderson model (i.e., the case when b (u) = λ u ) starting from the Dirac delta measure. [ABSTRACT FROM AUTHOR]

This article is concerned with the stability, ergodicity and mixing of invariant measures of a class of stochastic lattice plate equations with nonlinear damping driven by a family of nonlinear white noise. The polynomial growth drift term has an arbitrary order growth rate, and the diffusion term is a family of locally Lipschitz continuous functions. By modifying and improving several energy estimates of the solutions uniformly for initial data when time is large enough, we prove that the noise intensity union of all invariant measures of the stochastic equation is tight on ℓ 2 × ℓ 2 . Then, we show that the weak limit of every sequence of invariant measures in this union must be an invariant measure of the corresponding limiting equation under the locally Lipschitz assumptions on the drift and diffusion terms. Under some globally Lipschitz conditions on the drift and diffusion terms, we also prove that every invariant measure of the stochastic equation must be ergodic and exponentially mixing in the pointwise and Wasserstein metric sense. [ABSTRACT FROM AUTHOR]

Applying an invariant measure on phase space, we study the Koopman representation of a group of symplectomorphisms in an infinite-dimensional Hilbert space equipped with a translation-invariant symplectic form. The phase space is equipped with a finitely additive measure, invariant under the group of symplectomorphisms generated by Liouville-integrable Hamiltonian systems. We construct an invariant measure of Lebesgue type by applying a special countable product of Lebesgue measures on real lines. An invariant measure of Banach type is constructed by applying a countable product of Banach measures (defined by the Banach limit) on real lines. One of the advantages of an invariant measure of Banach type compared to an invariant measure of Lebesgue type is finiteness of the values of this measure in the entire space. The introduced invariant measures help us to describe both the strong continuity subspaces of the Koopman unitary representation of an infinite-dimensional Hamiltonian flow and the spectral properties of the constraint generator of the unitary representation on the invariant strong continuity subspace. [ABSTRACT FROM AUTHOR]

Asymptotic behavior of the three-dimensional stochastic Navier-Stokes equations with Markovian switching for additive noises is studied for an incompressible fluid flow in a bounded domain. The objective of this article is to prove the existence and identification of a stationary measure for such stochastic systems. To achieve this goal, a family of regularized equations is introduced in order to investigate the asymptotic behavior of their solutions. The existence of an ergodic measure for the regularized system is established by the Krylov-Bogolyubov method. The existence and identification of a stationary measure corresponding to the original system are obtained as a sequential limit point of the family of the ergodic measures that correspond to the regularized systems. The main result of this work is that under mild integrability conditions on the initial data and external force, there exists a stationary measure for the solution of the three-dimensional stochastic Navier-Stokes equations with Markovian switching. [ABSTRACT FROM AUTHOR]

In this paper, we study the long term dynamics of the stochastic Schrödinger delay lattice systems when the nonlinear drift and diffusion terms are both locally Lipschitz continuous. Based on the well-posedness of the system, we first prove the existence and uniqueness of weak pullback mean random attractors in a product Hilbert space. We then show the tightness of distribution laws of solutions and the existence of invariant measures. We further prove the set of all invariant measures of the delay system is tight and every limit point of invariant measures of the delay system must be an invariant measure of the limiting system as time delay approaches zero. The idea of uniform tail-estimates is employed to to establish the tightness of distributions of solutions as well as the set of invariant measures of the delay system. [ABSTRACT FROM AUTHOR]

This paper is mainly concerned with the asymptotic dynamics of non-autonomous stochastic 3D globally modified Navier–Stokes equations driven by nonlinear noise. Based on the well-posedness of such equations, we first show the existence and uniqueness of weak pullback mean random attractors. Then we investigate the existence of (periodic) invariant measures, the zero-noise limit of periodic invariant measures and their limit as the modification parameter N → N 0 ∈ (0 , + ∞) . Furthermore, under weaker conditions, we obtain the existence of invariant measures as well as their limiting behaviors when the external term is independent of time. Finally, by using weak convergence method, we establish the large deviation principle for the solution processes. [ABSTRACT FROM AUTHOR]

This paper is concerned with the dynamics of stochastic lattice systems with Markovian switching. Based on the well-posedness of solutions, we first prove the ergodicity of invariant measures and show that the Markov chain facilitates the existence of invariant measures. In order to investigate numerical invariant measures, the convergence of invariant measures is considered between the original systems and their finite-dimensional truncated systems. Due to this, we can use the backward Euler-Maruyama method to approximate invariant measures for such infinite-dimensional systems. This work provides a feasible path for the convergence of the finite-dimensional numerical invariant measures to the analytical invariant measure. [ABSTRACT FROM AUTHOR]

This paper deals with the asymptotic behavior of complex stochastic lattice systems driven by superlinear noise. We first prove the well-posedness and the existence of weak mean random attractors of the systems. We then show the existence of periodic measures and the weak compactness of the set of all periodic measures when a parameter varies in a bounded interval. We finally examine the limiting behavior of the periodic measures and in particular prove that every limit of periodic measures of the stochastic Ginzburg–Landau lattice system must be a periodic measure of the stochastic Schrödinger lattice system. [ABSTRACT FROM AUTHOR]

This work is devoted to stochastic reaction-diffusion lattice system driven by Lévy noises when the drift and diffusion terms are locally Lipschitz continuous. First, we investigate the existence and uniqueness of solutions of such system as well as weak pullback mean random attractors. Then the existence of periodic measures is obtained by the idea of uniform tail-estimates and Krylov-Bogolyubov's method. Under further conditions, we establish the uniqueness and the exponentially mixing property of periodic measure. Finally, the limit behavior of periodic measures is investigated for stochastic lattice system driven by Lévy noises with respect to noise intensities. [ABSTRACT FROM AUTHOR]

The present work is concerned with two-dimensional stochastic subcritical and critical convective Brinkman-Forchheimer (2 D SCBF) equations perturbed by a white noise (non-degenerate) in smooth bounded domains in R 2. We establish two important properties of the Markov semigroup associated with the solutions of 2 D SCBF equations (for the absorption exponent r = 1, 2, 3), that is, irreducibility and strong Feller property. These two properties implies the uniqueness of invariant measures and ergodicity also. Then, we discuss the ergodic behavior of 2 D SCBF equations by providing a Large Deviation Principle (LDP) for the occupation measure for large time (Donsker-Varadhan), which describes the exact rate of exponential convergence. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the regular dynamics for the 3D delay Brinkman–Forchheimer (BF) equations. We first prove the existence, uniqueness and time-dependent property of regular tempered pullback attractors as well as the existence of invariant measures for the 3D BF equations with non-autonomous abstract delay. We then study the asymptotic autonomy of regular pullback attractors for the 3D BF equations with autonomous abstract delay. Finally, we discuss the upper semicontinuity of regular pullback attractors as the delay time approaches to zero for the 3D BF equations with variable delay and distributed delay. [ABSTRACT FROM AUTHOR]

Denote by X a Banach space and by T : X → X a bounded linear operator with non-trivial kernel satisfying suitable conditions. We consider the concepts of entropy—for T-invariant probabilities—and pressure for α -Hölder continuous potentials. We also prove the existence of ground states associated with those potentials (the limit when the temperature goes to zero), when the Banach space X is equipped with a Schauder basis. We also produce an example concerning weighted shift operators defined on the Banach spaces c 0 (R) and l p (R) , 1 ≤ p < + ∞ , where our results do apply. In addition, we prove the existence of calibrated sub-actions when the potential satisfies certain regularity conditions using properties of the so-called Mañé potential and we exhibit examples of selection at zero temperature and explicit sub-actions in the class of α -Hölder continuous potentials. [ABSTRACT FROM AUTHOR]

We derive stationary measures for certain zero-temperature random polymer models, which we believe are new in the case of the zero-temperature limit of the beta random polymer (that has been called the river delta model). To do this, we apply techniques developed for understanding the stationary measures of the corresponding positive-temperature random polymer models (and some deterministic integrable systems). More specifically, the article starts with a survey of results for the four basic beta-gamma models (i.e. the inverse-gamma, gamma, inverse-beta and beta random polymers), highlighting how the maps underlying the systems in question can each be reduced to one of two basic bijections, and that through an ‘independence preservation’ property, these bijections characterise the associated stationary measures. We then derive similar descriptions for the corresponding zero-temperature maps, whereby each is written in terms of one of two bijections. One issue with this picture is that, unlike in the positive-temperature case, the change of variables required is degenerate in general, and so whilst the argument yields stationary solutions, it does not provide a complete characterisation of them. On the other hand, this degeneracy does allow us to explain the appearance of atoms in the stationary measures of certain zero-temperature models. We also derive from our viewpoint various links between random polymer models, some of which recover known results, some of which are novel, and some of which lead to further questions. [ABSTRACT FROM AUTHOR]

The basic idea we use throughout this paper is to generalize the construction of the Cantor set as the attractor of an iterated function system $\big(f_0,\ f_1\big)$, replacing the classical functions acting on $ [0,1]$ via $f_0(x) =\frac{x}{3}$ and $f_1(x)= \frac{2}{3} + \frac{x}{3}$ with the new functions acting via $f_0(x)= \theta x$ and $f_1(x) = 1 - \theta + \theta x$, where $\theta \in \Big[0,\ \frac{1}{2} \Big]$ is an arbitrary number. We add to the schema two positive numbers $p_0, \ p_1$ such that $p_0 + p_1 = 1$, obtaining the iterated function system with probabilities $\big(f_0,\; f_1 ; \; p_0,\; p_1\big)$ which generates the invariant set (attractor) and the invariant measure, according to J. Hutchinson. The structure of the invariant set (genera-lized Cantor set) being known, we focus on the detailed computation of the invariant measure. At the end of the paper, we study the dependence upon the parameter $\theta$ of the invariant set and of the invariant measure. [ABSTRACT FROM AUTHOR]

We investigate the existence of a weak martingale solution for a two-dimensional critical viscoelastic flow of the Oldroyd type driven by pure jump Lévy noise. Due to the viscoelastic nature, noise in the equation modeling stress tensor is considered in the Marcus canonical form. Owing to the lack of dissipation and taking into account of the structure of the non-linear terms, the proof requires higher order estimates. [ABSTRACT FROM AUTHOR]

We develop a dynamical approach to infinite volume directed polymer measures in random environments. We define polymer dynamics in 1 + 1 dimension as a stochastic gradient flow on polymers pinned at the origin, for energy involving quadratic nearest neighbor interaction and local interaction with random environment. We prove existence and uniqueness of the solution, continuity of the flow, the order-preserving property with respect to the coordinatewise partial order, and the invariance of the asymptotic slope. We establish ordering by noise which means that if two initial conditions have distinct slopes, then the associated solutions eventually get ordered coordinatewise. This, along with the shear-invariance property and existing results on static infinite volume polymer measures, allows to prove that for a fixed asymptotic slope and almost every realization of the environment, the polymer dynamics has a unique invariant distribution given by a unique infinite volume polymer measure, and, moreover, One Force—One Solution principle holds. We also prove that every polymer measure is concentrated on paths with well-defined asymptotic slopes and give an estimate on deviations from straight lines. [ABSTRACT FROM AUTHOR]

This paper investigates a two-dimensional nonautonomous nonlocal Swift–Hohenberg equation with two kinds of kernels and studies the existence of invariant measures and statistical solutions, which are important research objects in the area of turbulence for fluid systems. The existence of weak solutions guarantees a norm-to-weak continuous process associated with the nonautonomous equation. We first prove the existence of the pullback attractor for the process via the pullback flattening. Then the unique existence of invariant measures is obtained by appropriate construction, so that the invariant measure is supported by this pullback attractor. This invariant measure is turned out to be exactly a statistical solution of the original nonlocal Swift–Hohenberg equation. [ABSTRACT FROM AUTHOR]

This paper is concerned with the well-posedness and dynamics of FitzHugh–Nagumo systems with variable delay defined on infinite lattices. We first prove the existence and uniqueness of solutions as well as the existence of an evolution process for this system. We then establish the existence of tempered pullback attractors and invariant measures. Finally, we study the upper semicontinuity of pullback attractors as the delay time tends to zero. [ABSTRACT FROM AUTHOR]

We investigate the long-time behavior of solutions to a stochastically forced one-dimensional Navier–Stokes system, describing the motion of a compressible viscous fluid, in the case of linear pressure law. We prove existence of an invariant measure for the Markov process generated by strong solutions. We overcome the difficulties of working with non-Feller Markov semigroups on non-complete metric spaces by generalizing the classical Krylov–Bogoliubov method, and by providing suitable polynomial and exponential moment bounds on the solution, together with pathwise estimates. [ABSTRACT FROM AUTHOR]

We consider a modified Euler equation on ℝ 2 . We prove existence of weak global solutions for bounded (and fast decreasing at infinity) initial conditions and construct Gibbs-type measures on function spaces which are quasi-invariant for the Euler flow. Almost everywhere with respect to such measures (and, in particular, for less regular initial conditions), the flow is shown to be globally defined. [ABSTRACT FROM AUTHOR]

We consider in this work a model conservative system subject to dissipation and Gaussian-type stochastic perturbations. The original conservative system possesses a continuous set of steady states and is thus degenerate. We characterize the long-time limit of our model system as the perturbation parameter tends to zero. The degeneracy in our model system carries features found in some partial differential equations related, for example, to turbulence problems. [ABSTRACT FROM AUTHOR]

The limiting behavior of stochastic evolution processes with small noise intensity ϵ is investigated in distribution-based approaches. Let μϵ be a stationary measure for stochastic process Xϵ with small ϵ and X0 be a semiflow on a Polish space. Assume that {μϵ: 0 < ϵ ⩽ ϵ0} is tight. Then all their limits in the weak sense are X0-invariant and their supports are contained in the Birkhoff center of X0. Applications are made to various stochastic evolution systems, including stochastic ordinary differential equations, stochastic partial differential equations, and stochastic functional differential equations driven by Brownian motion or Lévy processes. [ABSTRACT FROM AUTHOR]

We extend the reduction method of Juzvinskiĭ to non compact dynamics. We show that the method could be used to prove results on entropies of transformations on non compact metric or Polish spaces. This is illustrated in three situations. First we extend the results of P. Walters on transformations with complete positive entropy. Then we extend the Abramov-Rohlin addition formula of R. K. Thomas. Finally we use the addition formula to extend the results of Walters on the uniqueness of invariant measures with maximal entropy. [ABSTRACT FROM AUTHOR]

We study a skew product IFS on the cylinder defined by Baker-like maps associated to a finite family of potential functions and the doubling map. We show that there exist a compact invariant set with attractive behaviour and a random SRB measure whose support is in that set. We also study the IFS ergodic optimization problem for that finite family of potential functions and characterize the maximizing measures and the critical value through a discounting limit. This shows the connection between this maximization problem and the superior boundary of the compact invariant set, which is described as a graph of the solution of the Bellman equation. [ABSTRACT FROM AUTHOR]

We consider the problem of approximating numerically the moments and the supports of measures which are invariant with respect to the dynamics of continuous- and discrete-time polynomial systems, under semialgebraic set constraints. First, we address the problem of approximating the density and hence the support of an invariant measure which is absolutely continuous with respect to the Lebesgue measure. Then, we focus on the approximation of the support of an invariant measure which is singular with respect to the Lebesgue measure. Each problem is handled through an appropriate reformulation into a conic optimization problem over measures, solved in practice with two hierarchies of finite-dimensional semidefinite moment-sum-of-square relaxations, also called Lasserre hierarchies. Under specific assumptions, the first Lasserre hierarchy allows to approximate the moments of an absolutely continuous invariant measure as close as desired and to extract a sequence of polynomials converging weakly to the density of this measure. The second Lasserre hierarchy allows to approximate as close as desired in the Hausdorff metric the support of a singular invariant measure with the level sets of the Christoffel polynomials associated to the moment matrices of this measure. We also present some application examples together with numerical results for several dynamical systems admitting either absolutely continuous or singular invariant measures. [ABSTRACT FROM AUTHOR]

The stationary version of a modified definition of statistical solution for the three-dimensional incompressible Navier–Stokes equations introduced in a previous work is investigated. Particular types of such stationary statistical solutions and their analytical properties are addressed. Results on the support and carriers of these stationary statistical solutions are also given, showing in particular that they are supported on the weak global attractor and are carried by a more regular part of the weak global attractor containing Leray–Hopf weak solutions which are locally strong solutions. Two recurrence-type results related to these measures are also proved. [ABSTRACT FROM AUTHOR]