Global Strong and Weak Solutions to Nematic Liquid Crystal Flow in Two Dimensions

We consider the strong and weak solutions to the Cauchy problem of the inhomogeneous incompressible nematic liquid crystal equations in two dimensions. We first establish the local existence and uniqueness of strong solutions by using the standard domain expanding method, and then extend such local strong solution to be a global one, provided the initial density is away from vacuum and the initial direction field satisfies some geometric structure. The size of the initial data can be large. Based on such global existence results of strong solutions, by using compactness argument, we obtain the global existence of weak solutions with nonnegative initial density.