A Fredholm Alternative for Elliptic with Interior and Boundary Nonlinear Reactions

TL;DR

This paper develops a Fredholm alternative framework for nonlinear elliptic problems with interior and boundary nonlinearities, extending classical linear theory to a broader class of differential operators and boundary conditions.

Contribution

It introduces a nonlinear Fredholm alternative for elliptic problems, generalizing linear results and applying them to Steklov-Robin equations.

Findings

Established a Fredholm alternative for linear two-parameter eigenvalue problems.

Constructed a nonlinear Fredholm alternative based on the linear theory.

Applied the abstract results to Steklov-Robin Fredholm equations.

Abstract

In this paper we study the existence of solutions to the following generalized nonlinear two-parameter problem \begin{equation*} a(u, v) \; =\; \lambda\, b(u, m) + \mu\, m(u, v) + \varepsilon\, F(u, v), \end{equation*} for a triple $(a, b, m)$ of continuous, symmetric bilinear forms on a real separable Hilbert space $V$ and nonlinear form $F$. This problem is a natural abstraction of nonlinear problems that occur for a large class of differential operators, various elliptic pde's with nonlinearities in either the differential equation and/or the boundary conditions being a special subclass. First, a Fredholm alternative for the associated linear two-parameter eigenvalue problem is developed, and then this is used to construct a nonlinear version of the Fredholm alternative. Lastly, the Steklov-Robin Fredholm equation is used to exemplify the abstract results.