Characterization of a low frequency power spectral density f−γ in a threshold model

This study investigates the modifications of the thermal spectrum, at low frequency, induced by an external damping on a system in heat contact with internal fluctuating impurities. Those impurities can move among locations and their oscillations are associated with a loss function depending on the model. The fluctuation properties of the system are provided by a potential function shaped by wells, in such a way that jumps between the stationary positions are allowed. The power spectral density associated with this dissipation mechanism shows a f−γ tail. The interest of this problem is that many systems are characterized by a typical f−γ spectral tail at low frequency. The model presented in this article is based on a threshold type behaviour and its generality allows applications in several fields. The effects of an external force, introduced to produce damping, are studied by using both analytical techniques and numerical simulations. The results obtained with the present model show that no reduction of the power spectral density is appreciable below the main peak of the spectral density.