“…The well-posedness (local and global) as well as persistence of regularity have recently attracted attention of many mathematicians [2,3,5,9,10,12,13,15,17,23,24,26,28,30], starting with Chae [7] and Hou and Li [20] who proved the global existence of regular solutions for smooth initial data. More precisely, Chae showed the global existence for (u 0 , ρ 0 ) ∈ H 3 × H 3 while Hou and Li proved the same for initial datum in H 3 × H 2 .…”