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Deterministic and random attractors for a wave equation with sign changing damping

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 Added by Sergey Zelik V.
 Publication date 2019
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and research's language is English




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The paper gives a detailed study of long-time dynamics generated by weakly damped wave equations in bounded 3D domains where the damping exponent depends explicitly on time and may change sign. It is shown that in the case when the non-linearity is superlinear, the considered equation remains dissipative if the weighted mean value of the dissipation rate remains positive and that the conditions of this type are not sufficient in the linear case. Two principally different cases are considered. In the case when this mean is uniform (which corresponds to deterministic dissipation rates), it is shown that the considered system possesses smooth uniform attractors as well as non-autonomous exponential attractors. In the case where the mean is not uniform (which corresponds to the random dissipation rate, for instance, when this dissipation rate is generated by the Bernoulli process), the tempered random attractor is constructed. In contrast to the usual situation, this random attractor is expected to have infinite Hausdorff and fractal dimension. The simplified model example which demonstrates infinite-dimensionality of the random attractor is also presented.



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In this paper, we study the following Kazdan-Warner equation with sign-changing prescribed function $h$ begin{align*} -Delta u=8pileft(frac{he^{u}}{int_{Sigma}he^{u}}-1right) end{align*} on a closed Riemann surface whose area is equal to one. The solutions are the critical points of the functional $J_{8pi}$ which is defined by begin{align*} J_{8pi}(u)=frac{1}{16pi}int_{Sigma}| abla u|^2+int_{Sigma}u-lnleft|int_{Sigma}he^{u}right|,quad uin H^1left(Sigmaright). end{align*} We prove the existence of minimizer of $J_{8pi}$ by assuming begin{equation*} Delta ln h^++8pi-2K>0 end{equation*}at each maximum point of $2ln h^++A$, where $K$ is the Gaussian curvature, $h^+$ is the positive part of $h$ and $A$ is the regular part of the Green function. This generalizes the existence result of Ding, Jost, Li and Wang [Asian J. Math. 1(1997), 230-248] to the sign-changing prescribed function case. We are also interested in the blow-up behavior of a sequence $u_{varepsilon}$ of critical points of $J_{8pi-varepsilon}$ with $int_{Sigma}he^{u_{varepsilon}}=1, limlimits_{varepsilonsearrow 0}J_{8pi-varepsilon}left(u_{varepsilon}right)<infty$ and obtain the following identity during the blow-up process begin{equation*} -varepsilon=frac{16pi}{(8pi-varepsilon)h(p_varepsilon)}left[Delta ln h(p_varepsilon)+8pi-2K(p_varepsilon)right]lambda_{varepsilon}e^{-lambda_{varepsilon}}+Oleft(e^{-lambda_{varepsilon}}right), end{equation*}where $p_varepsilon$ and $lambda_varepsilon$ are the maximum point and maximum value of $u_varepsilon$, respectively. Moreover, $p_{varepsilon}$ converges to the blow-up point which is a critical point of the function $2ln h^{+}+A$.
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