Critical behavior near the uniaxial-to-biaxial phase transition in nematic liquid crystals

We discuss the critical behavior in the vicinity of the uniaxial-biaxial phase transition. In particular we investigate the consequences of a static cross coupling between the order parameter and the uniaxial director, and we demonstrate that this coupling introduces a very slowly decaying transient which explains why the expected $x-y$ exponents have not yet been seen experimentally. By application of a sufficiently strong magnetic field parallel to the uniaxial director this transient can be removed.