Radiation by an Unruh-DeWitt detector in oscillatory motion

Quantum radiated energy flux emitted by an Unruh-DeWitt (UD) detector, with the internal harmonic oscillator coupled to a massless scalar field, in linear oscillatory motion in (3+1) dimensional Minkowski space is studied by numerical methods. Our results show that quantum interference can indeed suppress the signal of the Unruh effect if the averaged proper acceleration is sufficiently low, but not in the regime with high averaged acceleration and short oscillatory cycle. While the averaged radiated energy flux over a cycle is always positive as guaranteed by the quantum inequalities, an observer at a fixed angle may see short periods of negative radiated energy flux in each cycle of motion, which indicates that the radiation is squeezed. This reveals another resemblance between the detector theory and the moving-mirror model.