Variational and Geometric Analysis for Quasilinear Elliptic Equations and Systems

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Autore principale: Borgia, Natalino
Natura: Preprint
Pubblicazione: 2026
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author Borgia, Natalino
author_facet Borgia, Natalino
contents In this thesis we focus on quasilinear elliptic systems driven by various nonlinear operators, such as the p-Laplacian, and nonlinear sources that are allowed to exhibit both subcritical and critical growth. We aim to establish the existence of solutions for perturbation of specific eigenvalue problems, by employing variational and topological methods. To establish existence results for autonomous systems of quasilinear PDEs in the spirit of the paper by Amann and Zehnder, we develop a local Morse theory for functional associated to quasilinear elliptic systems. By refining topological arguments introduced by Cingolani and Degiovanni in Banach product spaces, we establish the finiteness of the critical groups and we derive a Poincaré-Hopf formula in a Banach product space, in presence of both subcritical and critical nonlinear coupling. We also establish uniform boundedness results for anisotropic quasilinear systems, that are of interest within regularity theory. To show existence results for non-autonomous systems of quasilinear PDEs in the spirit of the paper of Landesman and Lazer, we consider the eigenvalue problem for quasilinear elliptic systems introduced by de Thélin. We prove the simplicity and isolation of the first eigenvalue lambda1. Furthermore, we show the existence of a sequence of eigenvalues by employing a suitable deformation lemma proved by Bonnet. Subsequently, we analyze new sufficient Landesman-Lazer type conditions within the framework of quasilinear elliptic systems. We also investigate the N-dimensional Euclidean Onofri inequality, established by Del Pino and Dolbeault for smooth functions with compact support. After extending this inequality to a suitable weighted Sobolev space, we exploit its connection with the Liouville equation on R^N to prove an equivalence with the sharp logarithmic Moser-Trudinger inequality on the unit ball of R^N.
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publishDate 2026
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spellingShingle Variational and Geometric Analysis for Quasilinear Elliptic Equations and Systems
Borgia, Natalino
Analysis of PDEs
26D10 35B06 35B34 35B45 35B65 35J50 35J60 35J62 35J70 35J92 46E30 46E35 47H11 47J30 58E05 58E35
In this thesis we focus on quasilinear elliptic systems driven by various nonlinear operators, such as the p-Laplacian, and nonlinear sources that are allowed to exhibit both subcritical and critical growth. We aim to establish the existence of solutions for perturbation of specific eigenvalue problems, by employing variational and topological methods. To establish existence results for autonomous systems of quasilinear PDEs in the spirit of the paper by Amann and Zehnder, we develop a local Morse theory for functional associated to quasilinear elliptic systems. By refining topological arguments introduced by Cingolani and Degiovanni in Banach product spaces, we establish the finiteness of the critical groups and we derive a Poincaré-Hopf formula in a Banach product space, in presence of both subcritical and critical nonlinear coupling. We also establish uniform boundedness results for anisotropic quasilinear systems, that are of interest within regularity theory. To show existence results for non-autonomous systems of quasilinear PDEs in the spirit of the paper of Landesman and Lazer, we consider the eigenvalue problem for quasilinear elliptic systems introduced by de Thélin. We prove the simplicity and isolation of the first eigenvalue lambda1. Furthermore, we show the existence of a sequence of eigenvalues by employing a suitable deformation lemma proved by Bonnet. Subsequently, we analyze new sufficient Landesman-Lazer type conditions within the framework of quasilinear elliptic systems. We also investigate the N-dimensional Euclidean Onofri inequality, established by Del Pino and Dolbeault for smooth functions with compact support. After extending this inequality to a suitable weighted Sobolev space, we exploit its connection with the Liouville equation on R^N to prove an equivalence with the sharp logarithmic Moser-Trudinger inequality on the unit ball of R^N.
title Variational and Geometric Analysis for Quasilinear Elliptic Equations and Systems
topic Analysis of PDEs
26D10 35B06 35B34 35B45 35B65 35J50 35J60 35J62 35J70 35J92 46E30 46E35 47H11 47J30 58E05 58E35
url https://arxiv.org/abs/2605.31165