A non periodic and asymptotically linear indefinite variational problem in \(\mathbb{R}^N\)
Institución: Universidad de Brasilia, Brasil
Tipo de Evento: Researcher
A nonlinear Schrödinger equation which models a light beam
propagating in a saturable medium may present a sign changing
potential in the linear term and lead to a semilinear elliptic
equation in \(\mathbb{R}^N\) with a potential that has a negative
part, see [2]. We will present some recent results on the existence
of nontrivial solution for
\begin{equation*}
\begin{array}{lc} -\Delta u + V(x) u = f(u) & \quad{in} \
\mathbb{R}^N,
\end{array} \tag{\(P\)}
\end{equation*} \(N\geq 3\), with a non-periodic continuous potential
\(V\) which may change sign, with an asymptotic limit \(V_\infty\) at
infinity and a function \(f\) asymptotically linear at infinity.
We do not use projections on the Nehari manifold either apply the
generalized Nehari method as in [1]. We apply the classical linking
theorem with Cerami condition. This is possible by using the positive
ground state solution \(u_0\) of limit problem
\begin{equation*} -\Delta u + V_\infty u = f(u) \ \ \quad{in} \ \
\mathbb{R}^N, \tag{\(P_\infty\)}
\end{equation*} projected on a infinite dimensional subspace of
\({H^1(\mathbb{R}^N)}\) with finite codimension. Moreover, it is
crucial to estimate the interactions of the translates of \(u_0\) in
order to obtain the linking geometry. Furthermore, the lack of
compactness due to working with a problem in the unbounded domain
\(\mathbb{R}^N\) is circumvent by an assumption of a spectral gap of
the operator \(-\Delta + V\).
This is a work in collaboration with José Carlos de Oliveira
Jr. and Ricardo Ruviaro (UnB, Brazil).
[1] A. A. Pankov, Periodic nonlinear
Schrödinger equation with application to photonic crystals,
Milan J. Math., 73 (2005), 259--287.
[2] C. A. Stuart, Guidance properties of nonlinear
planar waveguides, Arch. Rational Mech. Anal.,
125 (1993), 145--200.