Special Variational Methods
I. A. Kuzin, Stanislav I. Pohožaev · Birkhäuser Basel eBooks · 1997
We saw in §12 that noncoercive problems 13.1 $$ - \Delta u + f({\text{x}},u) = 0\quad {\text{on}}\;{{\mathbb{R}}^{N}},u \to 0\quad \;{\text{as}}\;\left| {\text{x}} \right| \to \infty , $$ can be studied with the help of theorems on a conditional minimum if f is homogeneous. However such f are rare.