Dynamic correlations of macroscopic quantities.

The dynamics of fluctuations of a family of macroscopic quantities in one-dimensional systems (which includes the roughness and the total length of an interface, and the end-to-end distance of a filament) are analyzed. At thermodynamic equilibrium, the time-correlation function of these quantities can be expressed in terms of time-correlation functions of local quantities. In some cases, macroscopic quantities exhibit a universal diffusive behavior, which is not reached by local quantities.