Energy Dissipation and Regularity for a Coupled Navier-Stokes and Q-Tensor System

We study a complex non-newtonian fluid that models the flow of nematic liquid crystals. The fluid is described by a system that couples a forced Navier-Stokes system with a parabolic-type system. We prove the existence of global weak solutions in dimensions two and three. We show the existence of a Lyapunov functional for the smooth solutions of the coupled system and use the cancellations that allow its existence to prove higher global regularity, in dimension two. We also show the weak-strong uniqueness in dimension two

On formation of a locally self-similar collapse in the incompressible Euler equations

The paper addresses the question of existence of a locally self-similar blow-up for the incompressible Euler equations. Several exclusion results are proved based on the $L^p$-condition for velocity or vorticity and for a range of scaling exponents. In particular, in $N$ dimensions if in self-similar variables $u \in L^p$ and u \sim \frac{1}{t^{\a/(1+\a)}}, then the blow-up does not occur provided \a >N/2 or -1<\a\leq N/p. This includes the $L^3$ case natural for the Navier-Stokes equations. For \a = N/2 we exclude profiles with an asymptotic power bounds of the form |y|^{-N-1+\d} \lesssim |u(y)| \lesssim |y|^{1-\d}. Homogeneous near infinity solutions are eliminated as well except when homogeneity is scaling invariant.Comment: A revised version with improved notation, proofs, etc. 19 page

Analyticity and Decay Estimates of the Navier-Stokes Equations in Critical Besov Spaces

In this paper, we establish analyticity of the Navier-Stokes equations with small data in critical Besov spaces . The main method is Gevrey estimates, the choice of which is motivated by the work of Foias and Temam (Contemp Math 208:151-180, 1997). We show that mild solutions are Gevrey regular, that is, the energy bound holds in , globally in time for p &lt; a. We extend these results for the intricate limiting case p = a in a suitably designed E (a) space. As a consequence of analyticity, we obtain decay estimates of weak solutions in Besov spaces. Finally, we provide a regularity criterion in Besov spacesclose8