Quantum Measurements in a Finite Space–Time Domain

Abstract

In this paper, we discuss the quantum Unruh–DeWitt detector, which couples to the field bath for a finite amount of its proper time. It is demonstrated that due to the renormalization procedure, a new dimensionful parameter appears, having the meaning of a detector’s recovery proper time. It plays no role in the leading order of the perturbation theory, but can be important non-perturbatively. We also analyze the structure of finite time corrections in two cases—perturbative switching on, and switching off when the detector is thermalized.