On the regularity criterion of weak solutions for the 3D MHD equations

The paper deals with the 3D incompressible MHD equations and aims at improving a regularity criterion in terms of the horizontal gradient of velocity and magnetic field. It is proved that the weak solution (u, b) becomes regular provided that (del(h)u, del(h)b) is an element of L-8/3 (0, T; (B) over dot(infinity,infinity)(-1)(R-3)). The result is an extension of regularity criterion for 3D Navier-Stokes equations in Besov space due to Fang and Qian (Commun Pure Appl Anal 13: 585-603, 2014) [see also (Ni et al. in J Math Anal Appl 396:108-118, 2012)].