Nanostructures are among the most actively studied systems in present day - search. Theoretical and experimental studies of these small systems have unc- ered remarkable phenomena due to fundamental interactions and the reduction in dimensionality. Such nanostructures can be made out of well known ma- rials such as metals or semiconductors by lithographic procedures. In addition, novel material systems, e.g. semiconducting heterostructures, or even molecul- like materials, e.g. carbon nanotubes, can represent nanostructures in which electron-electron interactions are of importance. The discoveries of quantum Hall e?ects o?ered an initial glimpse into the striking phenomena that may occur in these low-dimensional structures. - tensive research since then, made possible by enormous advances in fabrication technologies, have revealed a large class of unexpected behaviors in nanostr- tures. The rapid technological progress in the last two decades has led to great excitement among both applied and basic physicists.The hope that miniat- ization of such devices will lead to a new age of smaller and faster computers has motivated extensive work, trying to understand the basic physics involved, an imperative step towards any future application.
