  In this paper the 3D Maxwell theory with single-sided planar boundary is
studied. As a consequence of the existence, on the boundary, of two Ward
identities, we find two chiral conserved edge currents satisfying a
Ka\c{c}-Moody algebra with central charge equal to the inverse of the Maxwell
coupling constant. We show that the boundary degrees of freedom are two 2D
scalar chiral bosons whose chiralities depend on the parameters of the bulk
Maxwell theory. In particular, the edge chiral bosons may have opposite
chiralities, in close analogy with the "spinon" and "holon" currents
characterizing the 3D topological insulators.
