Neumann problem for p-Laplace equation in metric spaces using a   variational approach: existence, boundedness, and boundary regularity
  We employ a variational approach to study the Neumann boundary value problem for the $p$-Laplacian on bounded smooth-enough domains in the metric setting, and show that solutions exist and are bounded. The boundary data considered are Borel measurable bounded functions. We also study boundary continuity properties of the solutions. One of the key tools utilized is the trace theorem for Newton-Sobolev functions, and another is an analog of the De Giorgi inequality adapted to the Neumann problem. 
Luk\'a\v{s} Mal\'y, Nageswari Shanmugalingam
math.MG math.AP