Neumann problem Dirichlet problem 10 Cuspidal domains 6 Thin domains 6 Nonlocal equations 4 Regularity 4 Traces 4 nonlocal equations 4 45A05 2 45C05 2 45M05 2 Approximation algorithms 2 Boundary value problems 2 Cauchy problem 2 Dirichlet condition 2 Error analysis 2 Finite element method 2 Finite elements 2 Fractional Laplacian 2 Fractional Sobolev spaces 2 Fractional equation 2 Graded meshes 2 Nonlocal fractional equations 2 Open bounded subsets 2 P-Laplacian 2 Perforated domains 2 Problem solving 2 Rate of convergence 2 Sobolev spaces 2 asymptotic analysis 2