Anomalies in the specific heat of a free damped particle: The role of   the cutoff in the spectral density of the coupling
  The properties of a dissipative system depend on the spectral density of the coupling to the environment. Mostly, the dependence on the low-frequency behavior is in the focus of interest. However, in order to avoid divergencies, it is also necessary to suppress the spectral density of the coupling at high frequencies. Interestingly, the very existence of this cutoff may lead to a mass renormalization which can have drastic consequences for the thermodynamic properties of the dissipative system. Here, we explore the role which the cutoff in the spectral density of the coupling plays for a free damped particle and we compare the effect of an algebraic cutoff with that of a sharp cutoff. 
Benjamin Spreng, Gert-Ludwig Ingold, Ulrich Weiss
cond-mat.stat-mech