Thermodynamic manifestations of structure fluctuations in liquids

The fluctuations of pressure and internal energy in a low-temperature liquids were analyzed. The fluctuations were generated by structure fluctuations and were related in a general and straightforward way to the differences between the long- and short-time thermodynamic susceptibilities. It was shown that the relations are similar to, but not identical with, those between thermodynamic fluctuations and susceptibilities in classical statistical mechanics. The derivation was based on the assumption that the local structure is a slow-relaxing mode in low-temperature liquids and may be characterized by an order parameter.