Critical Fluctuations near a Nematic-Smectic-A-Smectic-CMulticritical Point

Abstract
We report a high-resolution x-ray study of the fluctuations in a system exhibiting nematic, smectic-A, and smectic-C phases, with emphasis on the NAC multicritical region. We find that the transverse mass density fluctuations are always Lorentzian in character in explicit disagreement with the Lifshitz model for this system. Unexpectedly, both the mass density fluctuations and the tilt order parameter exhibit isotropic heliumlike critical exponents near the NAC point.