On the ideal low-frequency spatial filtration of the electrical potential at infinity

It is proved that for any physical system with localized voltage input the potential at infinity is the arithmetic average of the given input potentials. This is relevant to the topic of grounding of a system. In terms of spatial filtering, which is becoming a more and more important concept in modern system theory, we have here ideal filtration of the dc component of the (spatial) input voltage “signal” (i.e., the set of the given input potentials) at “infinity” considered as the “filter's output”. A symmetry argument, helpful in numerical simulations, is considered. Some basic system-theory terms, important for the physical side, are carefully defined.