LONG-RANGE CORRELATIONS AND GENERIC SCALE-INVARIANCE IN CLASSICAL FLUIDS AND DISORDERED ELECTRON-SYSTEMS

Long-ranged, or power-law, behavior of correlation functions in both s pace and time is discussed for classical systems and for quantum syste ms at finite temperature, and is compared with the corresponding behav ior in quantum systems at zero temperature. The origin of the long-ran ged correlations is explained in terms of soft modes. In general, corr elations at zero temperature are of longer range than their finite-tem perature or classical counterparts. This phenomenon is due to addition al soft modes that exist at zero temperature.