C. Papenfuss, R. Ellinghaus and W. Muschik
Derivation of a differential equation for a cholesteric liquid
crystal in electric fields
Mol. Cryst. Liq. Cryst. 192, 1990, 329-333
Lius lemma and some additional equilibrium conditions are used to
calculate the stress tensor of a liquid crystal in electromagnetic
fields. With the resulting constitutive equations, the balance of
moment of momentum in equilibrium yields the differential equation for
the director field. The example of a distorted cholesteric helix is
treated. The resulting equation is the same one, De Gennes derived
another way.