How often does the Unruh-DeWwitt detector click beyond four dimensions? (Q2872257)

This paper discusses the notion of a particle in Minkowski spacetime related to measurements made by inertial observers. The idea of a particle seen by an observer is described by a model of an interaction potential which includes a switching function to turn the interaction on and off. The calculations are carried out in \(d\)-dimensional Minkowski spacetime \(( d< 7)\) and is restricted to linear perturbation theory. The coupling of the quantum field to the observer is known as a Unruh-De-Witt detector and the transitions between the detector's quantum states are regarded as absorption and emissions of particles. The switching function is considered as the limit of a smooth function and the limit taken to a step function for a sharp turn on and turn off. The conclusions are that in this model the instantaneous transition rates are well defined up to \(d=5\) but for \(d=6\) the model needs to be restricted to a class of trajectories.