Abstract
The radiation-reaction force $mathcal{F}$ (t) acting on a moving mirror in a one-dimensional model is obtained by appeal to the fluctuation-dissipation theorem. Causality is found to provide the link between the dissipative and reactive forces; it is implemented by requirements of analyticity for the Fourier transform of the response function that links the mean force $mathcal{F}$ (t) to the velocity β (t) of the mirror. Particular attention is given to the issue of the divergent mass renormajization arising from the reactive part of the force, detected in some earlier treatments and denied in others