Multiplicity and solution construction in linear elliptic problems with nonlocal nonlinearities

This work investigates linear elliptic equations with multiple nonlocal nonlinearities in a bounded domain, which takes the form \begin{equation*} -\nabla\cdot(\od\nabla u) +\lambda fu= \eta \sum_{j=1}^kh_j\boldsymbol{\mathsf{N}}_j[u]+h_0. \end{equation*} Here $\lambda$ and $\eta$ are positive parameters, and $\boldsymbol{\mathsf{N}}_j[u]$ represents a nonlocal term dependent on the unknown solution~$u$. All coefficients are defined in the context of a wide range of applications. As such equations generally lack a variational structure, a new approach is developed that combines fixed-point arguments with asymptotic techniques. This method establishes the existence and multiplicity of solutions under specific conditions. Of particular interest is the role of the nonlocal nonlinearities, which lead to diverse structures of solutions. To the best of our knowledge, this property is a new finding not typically observed in related nonlocal elliptic problems.