Mathematical Analysis of Nematic Liquid Crystals and L-infinity Variational Problems

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The problems to be solved in this project are not only very challenging mathematically but also have strong connections and profound applications to other fields such as fluid mechanics and complex fluids, applied physics and material sciences, and control engineering.  Rigorous analysis of both the existence and the smoothness of certain kinds solutions to our models can predict the formation of singularities, allow researchers to gain insights into the turbulence phenomena, and justify both computational and experimental studies made by applied scientists and engineers. The proposed problems in the project will also serve as tools to train graduate students, and constitute as main parts of future research monographs aimed at both advanced graduate students and researchers.The technical side of this project is to study analytic issues in the three parts: (i) the hydrodynamic flow of nematic liquid crystals, (ii) variational problems on both liquid crystal droplets and the isotropic-nematic phase transitions in liquid crystals, and (iii) the L-infinity variational problems. The first part  deals with the Ericksen-Leslie system modeling the hydrodynamics of nematic liquid crystals, which is a strongly nonlinear-coupled system between the incompressible Navier-Stokes equation of the underlying fluid velocity field and the transported heat flow of harmonic maps for the orientation director field of the nematic liquid crystal molecules. The objective is to establish existence and partial regularity for Leray-Hopf type weak solutions in dimension three for arbitrary large initial data. The second part investigates both existence and classification of possible optimal configuration in the liquid crystal droplets and the formation of sharp interface between the isotropic and nematic phases by employing the Ericksen's model of variable degree of orientations for uniaxial nematic liquid crystals. The third part is to study the uniqueness of Aronsson's equations or absolute minimizers of L-infinity functionals that involve Hamiltonian functions with spatial dependence, the regularity of viscosity solutions to general Aronsson's equations, and the Liouville property of infinity harmonic functions in any dimension. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.