We are concerned with the size of the regular set for weak solutions
to the Navier–Stokes equations. It is shown that if a weighted
norm
of initial data is finite, the suitable weak solutions are regular in a set above a
space-time hypersurface determined by the degree of the weight. This result refines
and generalizes Theorems C and D of Caffarelli, Kohn and Nirenberg (Comm. PureAppl. Math. 35:6 (1982), 771–831) in various aspects. Our main tool is an
-regularity
theorem in terms of initial data, which is of independent interest. As applications, we
also study energy concentration near a possible blow-up time and regularity for
forward discretely self-similar solutions.
Keywords
Navier–Stokes equations, $\epsilon$-regularity, regular
set, energy concentration, discretely self-similar
solutions