In this paper, we consider the 3D Navier–Stokes equations in the whole space. We investigate some new inequalities and a priori estimates to provide the critical regularity criteria in terms of one directional derivative of the velocity field, namely,
∂3bold-italicu∈Lpfalse(false(0,Tfalse);Lqfalse(ℝ3false)false),
2p+3q=2,
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