From the Q-tensor flow for the liquid crystal to the Harmonic map flow

In this paper, we consider the solutions of the relaxed Q-tensor flow in $\R^3$ with small parameter $ε$. Firstly, we show that the limiting map is the so called harmonic map flow; Secondly, we also present a new proof for the global existence of weak solution for the harmonic map flow in three dimensions as in \cite{struwe88} and \cite{keller}, where Ginzburg-Landau approximation approach was used.