  In this paper we introduce the spectral approach to delocalization in
infinite disordered systems and provide a physical interpretation in context of
the classical model of Edwards and Thouless. We argue that spectral analysis is
an important contribution to localization problems since it avoids issues
related to the use of boundary conditions. Applying the method to 2D and 3D
numerical simulations with various amount of disorder W shows that
delocalization occurs for W<=0.6 in 2D and for W<=5 for 3D.
