A new study of the Unruh effect

We revisit the Unruh effect within a general framework based on direct, probability-level calculations. We rederive the transition rate of a uniformly accelerating Unruh–DeWitt monopole detector coupled to a massive scalar field, from both the perspective of an inertial (Minkowski) observer and an accelerating (Rindler) observer. We show that, for a measurement at a finite time after the initial state is prepared, the two perspectives give the same transition rate. We confirm that an inertial detector in a thermal bath of Minkowski particles responds differently to the accelerated detector (which perceives a thermal bath of Rindler particles), except in the case of a massless field where there is agreement at all times. Finally, new numerical results for the transition rate are presented and explained, highlighting the transient effects caused by forcing the field to initially be in the Minkowski vacuum state.