Nonexistence of Positive Supersolutions of Nonlinear Biharmonic Equations without the Maximum Principle

Abstract

We study classical positive solutions of the biharmonic inequality $-{\Delta }^{2}v\ge f(v)$ in exterior domains in ${\mathbb{R}}^n$ where $f:(0,\infty )\to (0,\infty )$ is continuous function. We give lower bounds on the growth of $f(s)$ at $s=0$ and/or $s=\infty$ such that this inequality has no $C^4$ positive solution in any exterior domain of ${\mathbb{R}}^n$. Similar results were obtained by Armstrong and Sirakov [ Nonexistence of positive supersolutions of elliptic equations via the maximum principle, Comm. Partial Differential Equations 36 (2011) 2011-2047] for $-\Delta v\ge f(v)$ using a method which depends only on properties related to the maximum principle. Since the maximum principle does not hold for the biharmonic operator, we adopt a different approach which relies on a new representation formula and an a priori pointwise bound for nonnegative solutions of $-{\Delta }^{2}u\ge 0$ in a punctured neighborhood of the origin in ${\mathbb{R}}^n$.

36 pages