Global existence and regularity for the full coupled Navier-Stokes and Q-tensor system

TL;DR

This paper establishes the global existence and regularity of solutions for a coupled Navier-Stokes and Q-tensor system modeling nematic liquid crystals, including the full system without simplifying assumptions, and analyzes the growth of solution norms.

Contribution

It extends previous work by analyzing the full coupled system without the zero-parameter assumption, providing new estimates and proving global weak solutions and regularity results.

Findings

Global weak solutions exist in 2D and 3D.

In 2D, solutions exhibit at most quadruply exponential growth in high norms.

Weak-strong uniqueness holds in 2D.

Abstract

We study the global existence and regularity of solutions for a system describing the evolution of a nematic liquid crystal fluid. The fluid is described by a system that couples a forced Navier-Stokes system with a parabolic-type system. In our previous work, \cite{pz1}, we assumed that a certain parameter, $\xi$, is zero, which had the effect of cancelling certain terms. In the current work we do not make this assumption and study the full system, observing that the presence of these additional terms has a non-trivial effect, namely the quadruply exponential increase of the high norms. We also estimate differently certain terms already existent in the simplified system and improve the estimates in \cite{pz1}. We prove the existence of global weak solutions in dimensions two and three. In dimension two we prove the higher regularity of solutions and show that the high norms increase in time at most quadruply exponential. We also show the weak-strong uniqueness in dimension two.