0 Is there emitted radiation in Unruh effect ?

The thermal radiance felt by a uniformly accelerated detector/oscillator/atom– the Unruh effect [1] – is often mistaken to be some emitted radiation detectable by an observer/probe/sensor. Here we show by an explicit calculation of the energy momentum tensor of a quantum scalar field that, at least in 1+1 dimension, while a polarization cloud is found to exist around the particle trajectory, there is no emitted radiation from a uniformly accelerated oscillator in equilibrium conditions. Under nonequilibrium conditions which can prevail for non-uniformly accelerated trajectories or before the atom or oscillator reaches equilibrium, there is conceivably radiation emitted, but that is not what Unruh effect entails. Invited talk given by BLH at the Capri Workshop on Quantum Aspects of Beam Physics, Oct. 2000. To appear in the Proceedings edited by Pisin Chen (World Scientific, Singapore, 2001)