Microscopic observation of order-parameter fluctuations in critical binary fluids: Morphology, self-similarity, and fractal dimension

We report what we believe to be the first direct visual observations of order-parameter fluctuations near a critical point. The observation has been made in a number of binary fluids which belong to the same universality class as the 3D Ising model. New properties can be investigated, in particular, the morphology of the flucutations when they are considered as clusters. This analysis has demonstrated the self-similarity of the clusters and provided a measurement of a fractal exponent ${\mathrm{D}}_{\mathrm{f}}$=2.8±0.1. .AE