  The presence of chiral modes on the edges of quantum Hall samples is
essential to our understanding of the quantum Hall effect. In particular, these
edge modes should support ballistic transport and therefore, in a single
particle picture, be supported in the absolutely continuous spectrum of the
single-particle Hamiltonian. We show in this note that if a free fermion system
on the two-dimensional lattice is gapped in the bulk, and has a nonvanishing
Hall conductance, then the same system put on a half-space geometry supports
edge modes whose spectrum fills the entire bulk gap and is absolutely
continuous.
