Semi-linear cooperative elliptic systems involving Schr{ö}dinger operators: Groundstate positivity or negativity

Abstract

We study here the behavior of the solutions to a $2\times 2$ semi-linear cooperative system involving Schr\" odinger operators (considered in its variational form): $$LU:=(-\Delta +q(x))U=AU+\mu U+F(x,U)\mathrm{in}{\mathbb{R}}^N$$ $$U(x{)}_{|x|\to \infty }\to 0$$ where $q$ is a continuous positive potential tending to $+\infty$ at infinity; $\mu$ is a real parameter varying near the principal eigenvalue of the system; $U$ is a column vector with components $u_1$ and $u_2$ and $A$ is a square cooperative matrix with constant coefficient. $F$ is a column vector with components $f_1$ and $f_2$ depending eventually on $U$.