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On the existence of global solutions of a coupled nonlinear Klein-Gordon equations. (English) Zbl 0637.35055
We study the existence and uniqueness of weak solutions of the mixed problem for the coupled system $(*)\quad \partial^ 2u/\partial t^ 2-\Delta u+u-| v|^{\rho +2}| u|^{\rho} u=f_ 1;\quad \partial^ 2v/\partial t^ 2-\Delta v+v-| u|^{\rho +2}| v|^{\rho} v=f_ 2$ in $$\Omega\times]0,T[$$, where $$\Omega$$ is any open set of $${\mathbb{R}}^ n$$ and $$\rho$$ satisfies certain conditions.
We observe that the standard energy method to obtain solutions does not work for the system (*) because the nonlinear terms are negative. We determine the existence of solutions using the method of potential well introduced by D. H. Sattinger [Arch. Ration. Mech. Anal. 30, 148- 172 (1968; Zbl 0159.391)]. So the data belong to the stability set of (*) which implies that the norms of the data are small. The uniqueness is obtained with more restrictions on $$\rho$$ and n.
This paper is a continuation of our work [Ann. Mat. Pura Appl., IV. Ser. 146, 173-183 (1987; Zbl 0633.35053)], where we study the existence and uniqueness of weak solutions of the mixed problem for the system $\partial^ 2u/\partial t^ 2-\Delta u+| v|^{\rho +2}| u|^{\rho} u=f_ 1;\quad \partial^ 2v/\partial t^ 2-\Delta v+| u|^{\rho +2}| v|^{\rho} u=f_ 2.$
Reviewer: M.M.Miranda

##### MSC:
 35L70 Second-order nonlinear hyperbolic equations 35D05 Existence of generalized solutions of PDE (MSC2000) 35L20 Initial-boundary value problems for second-order hyperbolic equations 35B30 Dependence of solutions to PDEs on initial and/or boundary data and/or on parameters of PDEs