“…We believe that a better understanding of Schrödinger operators with such singular potentials (supported by fractal sets) might shed some additional light on the above problem. This was the main motivation for the present work, although the results obtained here might be of some relevance to the study of fractal antennae, apertures, screens, and transducers (see, e.g, [8,9,10,15,32,47] and the references therein), especially in the case of impedance (Robin) boundary conditions (see [19,33,34,35]).…”