  A formulation for transport in an inhomogeneous, interacting electron gas is
described. Electronic current is induced by a constraint condition imposed as a
vector Lagrange multiplier. Constrained minimization of the total energy
functional on the manifold of an arbitrary constant current leads to a
many-electron Schroedinger equation with a complex, momentum-dependent
potential. Constant current Hartree-Fock and Kohn-Sham approximations are
formulated within the method and application to transport for quantum wires is
developed. No appeal is made to near equilibrium conditions or other
approximations allowing development of a general ab initio electronic transport
formulation.
