Abstract
We consider the equation a(y)uxx+divy(b(y)▽yu)+c(y)u=g(y, u) in the cylinder (−l,l)×∑, being elliptic where b(y)>0 and hyperbolic where b(y)<0. We construct self-adjoint realizations in L2(∑) of the operatorAu= (1/a) divy(b▽yu)+(c/a) in the case ofb changing sign. This leads to the abstract problem uxx+Au=g(u), whereA has a spectrum extending to +∞ as well as to −∞. For l=∞ it is shown that all sufficiently small solutions lie on an infinite-dimensional center manifold and behave like those of a hyperbolic problem. Anx-independent cross-sectional integral E=E(u, ux) is derived showing that all solutions on the center manifold remain bounded forx→ ±∞. For finitel, all small solutionsu are close to a solutionũ on the center manifold such that ‖u(x)-ũ(x)‖ Σ ⩽Ce -α(1-|x|) for allx, whereC andα are independent ofu. Hence, the solutions are dominated by hyperbolic properties, except close to the terminal ends {±1}×∑, where boundary layers of elliptic type appear.
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Mielke, A. On nonlinear problems of mixed type: A qualitative theory using infinite-dimensional center manifolds. J Dyn Diff Equat 4, 419–443 (1992). https://doi.org/10.1007/BF01053805
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DOI: https://doi.org/10.1007/BF01053805
Key words
- Mixed type
- nonlinear elliptic-hyperbolic problem
- bounded solutions
- center manifolds
- weak normal hyperbolicity