An ultrasonic investigation of the critical behaviour of the elastic moduli near the smectic C-smectic A phase transition

Results for the frequency-temperature dependence of the elastic moduli and the longitudinal sound velocity near the S_C-S_A transition are reported. The measurements were made at frequencies in the range 0.15-27 MHz. The interpretation of the results obtained was made using the theory of critical dynamics taking into consideration the bare anisotropy.