Vp. Romanov et Sv. Ulyanov, ULTRASOUND IN THE ISOTROPIC-PHASE OF CHOLESTERIC LIQUID-CRYSTALS, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 281, 1996, pp. 187-204
The acoustical properties of cholesteric liquid crystals in the isotro
pic phase including the vicinity of the phase transition point to the
ordered phase are investigated. An interaction of fluctuating field of
the tensor order parameter with the sound wave is considered. In Gaus
sian approximation the contribution of fluctuating modes to the sound
velocity dispersion and attenuation is calculated. The obtained formul
ae are compared with ones for nematics in isotropic phase. It was foun
d that the difference between these results rises in the vicinity of t
he phase transition point. This difference is connected, on the one ha
nd, with the specific fluctuating spectrum and on the other hand with
the closing of the instability temperatures of some fluctuating modes
to the phase transition temperature T-c. The results are illustrated b
y the numerical calculations.