The main subject of this paper concerns the establishment of certain classes of initial data, which grant short time uniqueness of the associated weak Leray–Hopf solutions of the three dimensional Navier–Stokes equations. In particular, our main theorem that this holds for any solenodial initial data, with finite L_2(mathbb {R}^3) norm, that also belongs to certain subsets of {textit{VMO}}^{-1}(mathbb {R}^3). As a corollary of this, we obtain the same conclusion for any solenodial u_{0} belonging to L_{2}(mathbb {R}^3)cap mathbb {dot{B}}^{-1+frac{3}{p}}_{p,infty }(mathbb {R}^3), for any 3<p<infty . Here, mathbb {dot{B}}^{-1+frac{3}{p}}_{p,infty }(mathbb {R}^3) denotes the closure of test functions in the critical Besov space {dot{B}}^{-1+frac{3}{p}}_{p,infty }(mathbb {R}^3). Our results rely on the establishment of certain continuity properties near the initial time, for weak Leray–Hopf solutions of the Navier–Stokes equations, with these classes of initial data. Such properties seem to be of independent interest. Consequently, we are also able to show if a weak Leray–Hopf solution u satisfies certain extensions of the Prodi-Serrin condition on mathbb {R}^3 times ]0,T[, then it is unique on mathbb {R}^3 times ]0,T[ amongst all other weak Leray–Hopf solutions with the same initial value. In particular, we show this is the case if uin L^{q,s}(0,T; L^{p,s}(mathbb {R}^3)) or if it’s L^{q,infty }(0,T; L^{p,infty }(mathbb {R}^3)) norm is sufficiently small, where 3<p< infty , 1le s<infty and 3/p+2/q=1.
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