Modelling nonequilibrium macroscopic oscillators of interest to experimentalists

Recent developments in experimental Gravitational Waves (GW) detection have led to the emergence of concerns regarding the inconsistency of treating the appa-rati as equilibrium systems. Nonequilibrium considerations surface, for example, in examining the electronic feedback machinery that is used to damp and to sta-bilize GW oscillator-bar detectors, or when considering temperature gradients produced by high-powered lasers used in interferometric GWdetectors. Either way, the experimental apparatus often consists of an oscillator with a very high quality factor, subjected to some power supply, and capableof extraordinary sensitivity in length displacement. Two theoretical paradigms (with their advan-tages and disadvantages) are presented: one in which the oscillator is described by an ad hoc Langevin equation with memory, and one in which it is modelled by a deterministic one-dimensional chain of anharmonic oscillators. Within both, it is seen that GW experiments suggest entirely novel problems to theorists.