  Although many physical arguments account for using a modified definition of
time delay in multichannel-type scattering processes, one can hardly find
rigorous results on that issue in the literature. We try to fill in this gap by
showing, both in an abstract setting and in a short-range case, the identity of
the modified time delay and the Eisenbud-Wigner time delay in waveguides. In
the short-range case we also obtain limiting absorption principles, state
spectral properties of the total Hamiltonian, prove the existence of the wave
operators and show an explicit formula for the S-matrix. The proofs rely on
stationary and commutator methods.
