Toward the open question proposed by P.-L. Lions in \cite{ Lions96} concerning the propagation of regularities of density patch for viscous inhomogeneous flow, we first establish the global in time well-posedness of two-dimensional inhomogeneous incompressible Navier-Stokes system with initial density being of the form: $\eta_1{ \bf 1}_{ \Om_0}+\eta_2{ \bf 1}_{ \Om_0^c},$ for any pair of positive constants $(\eta_1,\eta_2),$ and for any bounded, simply connected $W^{ k+2,p}(\R^2)$ domain $\Om_0.$ We then prove that the time evolved domain $\Om(t)$ also belongs to the class of $W^{ k+2,p}$ for any $t>0.$ Thus in some sense, we have solved the aforementioned Lions' question %of density patch in \cite{ Lions96} in the two-dimensional case. Compared with our previous paper \cite{ LZ}, here we remove the smallness condition on the jump, $|\eta_1-\eta_2|,$ moreover, the techniques used in the present paper are completely different from those in \cite{ LZ}.
Categories: math.AP