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Abstract
The concept of rotational viscosities of smectic C and ferroelectric chiral smectic C* liquid crystals is reviewed. We give the expressions for the elastic torque, the rotational torque and the entropy production in spherical polar coordinates for smectic C and ferroelectric chiral smectic C* liquid crystals for pure rotational motion. Comparing these with the corresponding expressions for nematic liquid crystals, we show the way in which the rotational viscosity coefficients must be defined for smectic C and ferroelectric smectic C* liquid crystals in order to obtain consistency between the description of rotational motion of these systems and nematic liquid crystals.