## Numbers of zeros on invariant manifolds in reaction-diffusion equations.(English)Zbl 0594.35056

The ”orbit connection” problem for dynamical systems consists in establishing whether, given two (hyperbolic) rest points $$v_ 1$$, $$v_ 2$$, having a nontrivial unstable, respectively stable manifold, there is a solution u(t) (”orbit”) such that $$u(-\infty)=v_ 1$$, $$u(+\infty)=v_ 2$$. In the specific case of the dynamical system associated with a one- dimensional semilinear parabolic equation, an insight into this problem can be provided by the analysis of the number of sign changes of the solutions. This is indeed the main motivation for the present paper, in which bounds are established for an (appropriately defined) number of zeros of $$u(t)-v_ 1$$ and $$u(t)-v_ 2$$. The proofs involve two distinct tools: namely monotonicity methods and, on the other hand, a detailed analysis of the structure of the unstable and of the stable manifold of a hyperbolic stationary solution.
Reviewer: P.de Mottoni

### MSC:

 35K55 Nonlinear parabolic equations 80A20 Heat and mass transfer, heat flow (MSC2010) 35Q99 Partial differential equations of mathematical physics and other areas of application 35B40 Asymptotic behavior of solutions to PDEs
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### References:

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