AbstractThis paper deals with the existence of multiple solutions for the quasilinear equation-div𝐀(x,∇u)+|u|α(x)-2u=f(x,u) in ℝN,{-\operatorname{div}\mathbf{A}(x,\nabla u)+|u|^{\alpha(x)-2}u=f(x,u)\quad\text% {in ${\mathbb{R}^{N}}$,}}which involves a general variable exponent elliptic operator𝐀{\mathbf{A}}in divergence form. The problem corresponds to double phase anisotropic phenomena, in the sense that the differential operator has various types of behavior like|ξ|q(x)-2ξ{|\xi|^{q(x)-2}\xi}for small|ξ|{|\xi|}and like|ξ|p(x)-2ξ{|\xi|^{p(x)-2}\xi}for large|ξ|{|\xi|}, where1<α(⋅)≤p(⋅)<q(⋅)<N{1<\alpha(\,\cdot\,)\leq p(\,\cdot\,)<q(\,\cdot\,)<N}. Our aim is to approach variationally the problem by using the tools of critical points theory in generalized Orlicz–Sobolev spaces with variable exponent. Our results extend the previous works [A. Azzollini, P. d’Avenia and A. Pomponio, Quasilinear elliptic equations inℝN\mathbb{R}^{N}via variational methods and Orlicz–Sobolev embeddings, Calc. Var. Partial Differential Equations 49 2014, 1–2, 197–213] and [N. Chorfi and V. D. Rădulescu, Standing wave solutions of a quasilinear degenerate Schrödinger equation with unbounded potential, Electron. J. Qual. Theory Differ. Equ. 2016 2016, Paper No. 37] from cases where the exponentspandqare constant, to the case wherep(⋅){p(\,\cdot\,)}andq(⋅){q(\,\cdot\,)}are functions. We also substantially weaken some of the hypotheses in these papers and we overcome the lack of compactness by using the weighting method.
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