Weak-strong uniqueness of the full coupled Navier-Stokes and Q-tensor system in dimension three

Abstract: In this paper, we study the weak-strong uniqueness for the Leray-Hopf type weak solutions to the Beris-Edwards model of nematic liquid crystals in $\mathbb{R}^3$ with an arbitrary parameter $\xi\in\mathbb{R}$, which measures the ratio of tumbling and alignment effects caused by the flow. This result is obtained by proposing a new uniqueness criterion in terms of $(\Delta Q,\nabla u)$ with regularity $L_t^qL_x^p$ for $\frac{2}{q}+\frac{3}{p}=\frac{3}{2}$ and $2\leq p\leq 6$, which enable us to deal with the additional nonlinear difficulties arising from the parameter $\xi$. Comparing with the related literature, our finding also reveals a new regime of weak-strong uniqueness for the simplified case of $\xi=0$. Moreover, we establish the global well-posedness of this model for small initial data in $H^s$-framework.