Let
c be the usual mountain pass level for the semilinear elliptic functional
|
G(u) = \frac12 òW ( | Ñu | 2 + lu2)dx - òW F(x, u(x))dx. (0.1)G(u) = \frac{1}{2} \int_{\Omega} (\mid\nabla u\mid^{2} + \lambda u^{2})dx - \int_{\Omega} F(x, u(x))dx. \quad (0.1)
|
. In general,
c ≤
c#, where
c# is the analogous mountain pass level of the asymptotic functional
G# defined with respect to unbounded shifts or dilations. We show under general conditions that whenever the strict inequality
c ≤
c# holds, the functional
G satisfies the Palais – Smale condition at the level
c and, consequently, has a critical point at this level. This sets a solvability framework for
unconstrained mountain pass similar to that of P.-L.Lions set for constrained minimization. The nonlinearity
F is allowed to have critical growth with asymptotically selfsimilar oscillations about the critical “stem”
|u|2*|u|^{2*} and not only “stem” asymptotics. For example, the main existence result, Theorem 3.2, holds for
F(x, s) = |s|2* e\frac sN x21+x2 sin(2 log(|s|))F(x, s) = |s|^{2*} e^ {\frac {\sigma N x^{2}}{1+x^{2}} {\rm sin}(2 log(|s|))}. Since the unconstrained minimax is studied, the convexity-type conditions that arise with the use of Nehari constraint
(G¢(u), u) = 0(G'(u), u) = 0 are not required.
Mathematics Subject Classification (2000). Primary 35J20, 35J60 - Secondary 49J35
Keywords. Semilinear elliptic equations - concentration compactness - mountain pass - positive solutions - variational problems
Research done as a visitor at Ceremath, University of Toulouse 1.