Landau theory of the isotropic-nematic critical point

Landau theory is used to analyze the effect of an applied on nematics with positive dielectric (or diamagnetic) anisotropy. Analytic results are given for the phase boundary, stability limits, and location of the critical points in the field-temperature phase diagram. For biphenyl compounds having a dielectric anisotropy ?_a≈10, it is argued that the critical point should occur at E_c≈10² kV/cm, which is experimentally accessible.