  In order to specify a nonequilibrium steady state of a quantum wire (QWR),
one must connect reservoirs to it. Since reservoirs should be large 2d or 3d
systems, the total system is a large and inhomogeneous 2d or 3d system, in
which e-e interactions have the same strength in all regions. However, most
theories of interacting electrons in QWR considered simplified 1d models, in
which reservoirs are absent or replaced with noninteracting 1d leads. We first
discuss fundamental problems of such theories in view of nonequilibrium
statistical mechanics. We then present formulations which are free from such
difficulties, and discuss what is going on in mesoscopic systems in
nonequilibrium steady state. In particular, we point out important roles of
energy corrections and non-mechanical forces, which are induced by a finite
current.
