This paper investigates nonlinear fractional equations driven by the spectral fractional Laplacian under mixed Dirichlet-Neumann boundary conditions. It establishes nontrivial weak solutions through topological and variational methods, a localization argument, and explicit asymptotic estimates, with further criteria based on the Chebyshev radius of the domain.
Editorial status: Under review. The preprint is available on arXiv and HAL (hal-05685120).