On global solutions of quasilinear second-order elliptic inequalities

Abstract

We consider the inequality $$ - \operatorname{div} A (x, \nabla u) \ge f (u) \quad \mbox{in } {\mathbb R}^n, $$ where $n \ge 2$ and $A$ is a Caratheodory function such that $$ C_1 |\xi|^p \le \xi A (x, \xi) \quad \mbox{and} \quad |A (x, \xi)| \le C_2 |\xi|^{p-1} $$ with some constants $C_1 > 0$, $C_2 > 0$, and $p > 1$ for almost all $x \in {\mathbb R}^n$ and for all $\xi \in {\mathbb R}^n$. Our aim is to find exact conditions on the function $f$ guaranteeing that any non-negative solution of this inequality is identically zero.