Phase ordering of conserved vectorial systems with field-dependent mobility

The dynamics of phase-separation in conserved systems with an O(N) continuous symmetry is investigated in the presence of an order-parameter-dependent mobility M{?}=1-a?2. The model is studied analytically in the framework of the large-N approximation and by numerical simulations of the N=2, N=3, and N=4 cases in d=2, for both critical and off-critical quenches. We show the existence of a universality class for a=1 characterized by a growth law of the typical length L(t)~t1/z with dynamical exponent z=6 as opposed to the usual value z=4, which is recovered for a<1.