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 Title Asymptotic stability for the Klein Gordon equation on non compact Riemannian manifolds - A sharp result
 Name Marcelo M Cavalcanti Country Brazil Email mmcavalcanti@uem.br Co-Author(s) Valeria Cavalcanti, Cesar Bortot, Paolo Piccione Submit Time 2014-02-28 08:16:21 Session Special Session 60: Recent advances in evolutionary equations
 Contents The Klein Gordon equation subject to a nonlinear and locally distributed damping, posed in a complete and non compact $n$ dimensional Riemannian manifold $(\mathcal{M}^n,\mathbf{g})$ without boundary is considered. Let us assume that the dissipative effects are effective in $(\mathcal{M}\backslash \overline{\Omega}) \cup (\Omega \backslash V)$, where $\Omega$ is an arbitrary open bounded set with smooth boundary. In the present article we introduce a new class of non compact Riemannian manifolds, namely, manifolds which admit a smooth function $f$, such that the Hessian of $f$ satisfies the {\em pinching conditions} (locally in $\Omega$), for those ones, there exist a finite number of disjoint open subsets $V_k$ free of dissipative effects such that $\bigcup_k V_k \subset V$ and for all $\varepsilon>0$, $meas(V)\geq meas(\Omega)-\varepsilon$, or, in other words, the dissipative effect inside $\Omega$ possesses measure arbitrarily small. It is important to be mentioned that if the function $f$ satisfies the pinching conditions everywhere, then it is not necessary to consider dissipative effects inside $\Omega$.