  We use the technique of bosonization to understand a variety of recent
experimental results on the conductivity of a quantum wire. The quantum wire is
taken to be a finite-length Luttinger liquid connected on two sides to
semi-infinite Fermi liquids through contacts. The contacts are modeled as
(short) Luttinger liquids bounded by localized one-body potentials. We use
effective actions and the renormalization group to study the effects of
electronic interactions within the wire, the length of the wire, finite
temperature and a magnetic field on the conductivity. We explain the deviations
of the conductivity away from 2Ne^2/h in wires which are not too short as
arising from renormalization effects caused by the repulsive interactions. We
also explain the universal conductance corrections observed in different
channels at higher temperatures. We study the effects of an external magnetic
field on electronic transport through this system and explain why odd and even
spin split bands show different renormalizations from the universal conductance
values. We discuss the case of resonant transmission and of the possibility of
producing a spin-valve which only allows electrons of one value of the spin to
go through. We compare our results for the conductance corrections with
experimental observations. We also propose an experimental test of our model of
the contact regions.
