{ "id": "1609.05556", "version": "v1", "published": "2016-09-18T21:41:52.000Z", "updated": "2016-09-18T21:41:52.000Z", "title": "Compactness and existence results for the $p$-Laplace equation", "authors": [ "Marino Badiale", "Michela Guida", "Sergio Rolando" ], "comment": "This document is an expanded and complementary version of arXiv:1510.03879, and continues the work of arXiv:1403.3803 and arXiv:1506.00056", "categories": [ "math.AP" ], "abstract": "Given $10$, $r>0$, we define the weighted spaces \\[ W=\\left\\{ u\\in D^{1,p}(\\mathbb{R}^{N}):\\int_{\\mathbb{R}^{N}}V\\left( \\left| x\\right| \\right) \\left| u\\right| ^{p}dx<\\infty \\right\\} ,\\quad L_{K}^{q}=L^{q}(\\mathbb{R}^{N},K\\left( \\left| x\\right| \\right) dx) \\] and study the compact embeddings of the radial subspace of $W$ into $L_{K}^{q_{1}}+L_{K}^{q_{2}}$, and thus into $L_{K}^{q}$ ($=L_{K}^{q}+L_{K}^{q}$) as a particular case. We consider exponents $q_{1},q_{2},q$ that can be greater or smaller than $p$. Our results do not require any compatibility between how the potentials $V$ and $K$ behave at the origin and at infinity, and essentially rely on power type estimates of their relative growth, not of the potentials separately. We then apply these results to the investigation of existence and multiplicity of finite energy solutions to nonlinear $p$-Laplace equations of the form \\[ -\\triangle _{p}u+V\\left( \\left| x\\right| \\right) |u|^{p-1}u=g\\left( \\left| x\\right| ,u\\right) \\quad \\text{in }\\mathbb{R}^{N},\\ 1