Solutions of super-linear elliptic equations and their Morse indices

Abstract

We investigate here the degenerate bi-harmonic equation: $$Δ_{m}^2 u=f(x,u)\; \;\;\mbox{in} Ø,\quad u = Δu = 0\quad \mbox{on }\; \pΩ,$$ with $m\ge 2,$ and also the degenerate tri-harmonic equation: $$ -Δ_{m}^3 u=f(x,u)\;\;\; \mbox{in} Ø,\quad u = \frac{\p u}{\p ν} = \frac{\p^{2} u}{\pν^{2}} = 0\quad \mbox{on }\; \pΩ,$$ where $\Omega \subset {\mathbb{R}}^N$ is a bounded domain with smooth boundary $N>4$ or $N>6$ resp, and $f\in {\mathrm{C}}^1(\Omega \times \mathbb{R})$ satisfying suitable m-superlinear and subcritical growth conditions. Our main purpose is to establish $L^p$ and $L^{\infty }$ explicit bounds for weak solutions via the Morse index. Our results extend previous explicit estimate obtained in \cite{c, HHF, hyf, lec}.

arXiv admin note: text overlap with arXiv:1511.04907