Nils Ackermann
School of Mathematics and Statistics, University of Sydney
Equilibria and Connecting Orbits in Non-Dissipative Parabolic
Equations
Wednesday 12th April 14:05-14:55pm,
Carslaw Building Room 373.
For many years the existence of solutions of semilinear
elliptic equations on bounded domains has been investigated using
variational methods. If 0 is a solution and a superlinear term is
present then the celebrated "Mountain Pass Theorem" by Ambrosetti and
Rabinowitz and its variants usually yield at least one solution, in
many cases several or even infinitely many.
Here I present an alternative approach to the existence question for
the elliptic equation, replacing the gradient flow of the energy
functional by the flow of the associated parabolic problem. It turns
out that one can nicely combine the topological ideas of the
variational method with information on the geometric structure of
stable and unstable manifolds in the parabolic problem. Due to the
existence of blow-up in finite time the main difficulty here is the
compactness issue, which has been resolved recently by Pavol Quittner.
We obtain existence results for equilibria and connecting orbits, and
information on their nodal properties. There is no known variational
setting that yields the latter in the case of an indefinite
superlinear term.