Uniaxial rebound at the nematic biaxial transition

Over the last few years, renewed interest has been raised by the simplified general interaction models
proposed by Straley for mesogenic molecules possessing the D_2h symmetry and capable of producing biaxial
nematic order. It has already been shown that, in the presence of certain special symmetries, just two out of the
four order parameters that are in general necessary, suffice for the description of a biaxial phase. For some
other range of parameters, these reducing symmetries do not hold, and, moreover, a mean-field treatment has
to be suitably changed into a minimax strategy, still producing a transition to a low-temperature biaxial phase.
Upon studying the general parameter range, we identify as a common feature the behavior of a uniaxial order
parameter, attaining a local minimum at the biaxial-to-uniaxial transition temperature, and recognizably increasing
away from it. This finding is confirmed by a Monte Carlo simulation.