Two-Phase Robin Problem Incorporating Nonlinear Boundary Condition

This article focuses on the analysis of quasilinear equations influenced by the two-phase operator, commonly referred to as the ‘‘double-phase operator’’, while also incorporating a non-linear boundary condition. We prove the multiplicity of solutions through the utilization the method of Nehari manifold, complemented through the utilization of comparative techniques and critical point theory. Furthermore, determine the polarity of these solutions, distinctly identifying one as positive, another as negative, and a third as nodal.