Dynamics of Ordering of Isotropic Magnets

We study the dynamics of ordering of the nonconserved and conserved Heisenberg magnet. The dynamics consists of two parts - an irreversible dissipation into a heat bath and a reversible precession induced by a torque due to the local molecular field. For quenches both to T=0 and T=T_c, we show that the torque is irrelevant when the dynamics is nonconserved but relevant when the dynamics is conserved and is governed by a new nontrivial fixed point.Comment: 7 pages, 5 eps figures. To appear in Physica A as a part of the proceedings of the StatPhys - Calcutta III, January 1999, Calcutta, India. Largely a combination of Phys. Rev. E, {\bf 57}, (1998),5069 and cond-mat/9903041, together with a detailed discussion on multiscalin