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Register a new userSufficient and Necessary Criteria for Existence of Pullback Attractors for Non-compact Random Dynamical Systems
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Bixiang Wang
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We study pullback attractors of non-autonomous non-compact dynamical systems generated by differential equations with non-autonomous deterministic as well as stochastic forcing terms. We first introduce the concepts of pullback attractors and asymptotic compactness for such systems. We then prove a sufficient and necessary condition for existence of pullback attractors. We also introduce the concept of complete orbits for this sort of systems and use these special solutions to characterize the structures of pullback attractors. For random systems containing periodic deterministic forcing terms, we show the pullback attractors are also periodic. As an application of the abstract theory, we prove the existence of a unique pullback attractor for Reaction-Diffusion equations on $R^n$ with both deterministic and random external terms. Since Sobolev embeddings are not compact on unbounded domains, the uniform estimates on the tails of solutions are employed to establish the asymptotic compactness of solutions.
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The upper semicontinuity of random attractors for non-compact random dynamical systems is proved when the union of all perturbed random attractors is precompact with probability one. This result is applied to the stochastic Reaction-Diffusion with white noise defined on the entire space R^n.
In this article we study the asymptotic behavior of solutions, in sense of global pullback attractors, of the evolution system $$ begin{cases} u_{tt} +etaDelta^2 u+a(t)Deltatheta=f(t,u), & t>tau, xinOmega, theta_t-kappaDelta theta-a(t)Delta u_t=0, & t>tau, xinOmega, end{cases} $$ subject to boundary conditions $$ u=Delta u=theta=0, t>tau, xinpartialOmega, $$ where $Omega$ is a bounded domain in $mathbb{R}^N$ with $Ngeqslant 2$, which boundary $partialOmega$ is assumed to be a $mathcal{C}^4$-hypersurface, $eta>0$ and $kappa>0$ are constants, $a$ is an Holder continuous function, $f$ is a dissipative nonlinearity locally Lipschitz in the second variable.
We study the long time behavior of solutions of the non-autonomous Reaction-Diffusion equation defined on the entire space R^n when external terms are unbounded in a phase space. The existence of a pullback global attractor for the equation is established in L^2(R^n) and H^1(R^n), respectively. The pullback asymptotic compactness of solutions is proved by using uniform a priori estimates on the tails of solutions outside bounded domains.
The existence of a pullback attractor is established for the singularly perturbed FitzHugh-Nagumo system defined on the entire space $R^n$ when external terms are unbounded in a phase space. The pullback asymptotic compactness of the system is proved by using uniform a priori estimates for far-field values of solutions. Although the limiting system has no global attractor, we show that the pullback attractors for the perturbed system with bounded external terms are uniformly bounded, and hence do not blow up as a small parameter approaches zero.
The theory of random attractors has different notions of attraction, amongst them pullback attraction and weak attraction. We investigate necessary and sufficient conditions for the existence of pullback attractors as well as of weak attractors.
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