  The coarsening exponents describing the growth of long-range order in systems
quenched from a disordered to an ordered phase are discussed in terms of the
decay rate, omega(k), for the relaxation of a distortion of wavevector k
applied to a topological defect. For systems described by order parameters with
Z(2) (`Ising'), and O(2) (`XY') symmetry, the appropriate defects are domain
walls and vortex lines respectively. From omega(k) ~ k^z, we infer L(t) ~
t^(1/z) for the coarsening scale, with the assumption that defect relaxation
provides the dominant coarsening mechanism. The O(2) case requires careful
discussion due to infrared divergences associated with the far field of a
vortex line. Conserved, non-conserved, and `intermediate' dynamics are
considered, with either short-range or long-range interactions. In all cases
the results agree with an earlier `energy scaling' analysis.
