Bubble nucleation as seen by different observers

Pair production in a constant electric field is closely analogous to bubble nucleation false vacuum. The classical trajectories of the pairs are Lorentz invariant, but this invariance should be broken by process. Garriga et al. used model detector, consisting other particles interacting with pairs, investigate how pair seen different Lorentzian observers. They found that (antiparticles) predominantly observed moving direction (opposite to) and concluded observers see nucleating preferentially detector's rest frame. Here, we apply approach case where two detectors relative one another observe particle antiparticle same pair. We find each detector will still occur its frame, regardless motion detector. However, if velocity sufficiently high, can towards arbitrarily large momenta, contrary usual expectation.