Nematic liquid crystals and biaxiality

In nematic liquid crystals, rod-like molecules tend to align. Locally this alignment can exhibit uniaxial symmetry, or be biaxial. In certain regimes, a "biaxial escape" phenomenon is predicted. We show that the uniaxial symmetry constraint is very rigid independently of the regime: biaxial escape has to be more than the mere breaking of this symmetry. Then we present a rigorous interpretation of biaxial escape at low temperature (joint with Andres Contreras).