  While observations indicate that the predominant source of cosmic
inhomogeneities are adiabatic perturbations, there are a variety of candidates
to provide auxiliary trace effects, including inflation-generated primordial
tensors and cosmic defects which both produce B-mode cosmic microwave
background (CMB) polarization. We investigate whether future experiments may
suffer confusion as to the true origin of such effects, focusing on the ability
of Planck to distinguish tensors from cosmic strings, and show that there is no
significant degeneracy.
