Coarsening in a driven Ising chain with conserved dynamics

We study the low-temperature coarsening of an Ising chain subject to spin-e xchange dynamics and a small driving force. This dynamical system reduces t o a domain diffusion process, in which entire domains undergo nearest-neigh bor hopping, except for the shortest domains-dimers-which undergo long-rang e hopping. This system exhibits anomalous ordering dynamics due to the exis tence of two characteristic length scales: the average domain length L(t) s imilar to t(1/2) and the average dimer hopping distance l(t) similar to roo t L(t) similar to t(1/4). As a consequence of these two scales, the density of short domains decays as t(-5/4), instead of the t(-3/2) decay that woul d arise from pure domain diffusion. [S1063-651X(99)08109-X].