Observer dependence of bubble nucleation and Schwinger pair production

Abstract

Pair production in a constant electric field is closely analogous to bubble nucleation in a false vacuum. The classical trajectories of the pairs are Lorentz invariant, but it appears that this invariance should be broken by the nucleation process. Here, we use a model detector, consisting of other particles interacting with the pairs, to investigate how pair production is seen by different Lorentzian observers. We focus on the idealized situation where a constant external electric field is present for an infinitely long time, and we consider the in-vacuum state for a charged scalar field that describes the nucleating pairs. The in-vacuum is defined in terms of modes which are positive frequency in the remote past. Even though the construction uses a particular reference frame and a gauge where the vector potential is time dependent, we show explicitly that the resulting quantum state is Lorentz invariant. We then introduce a "detector" particle which interacts with the nucleated pairs, and show that all Lorentzian observers will see the particles and antiparticles nucleating preferentially at rest in the detector's rest frame. Similar conclusions are expected to apply to bubble nucleation in a sufficiently long lived vacuum. We also comment on certain unphysical aspects of the Lorentz invariant in-vacuum, associated with the fact that it contains an infinite density of particles. This can be easily remedied by considering Lorentz breaking initial conditions.

Schwinger mechanism revisited

“…based on the AdS/CFT correspondence) setups were considered in order to investigate particle production by external fields in the strong coupling regime [167][168][169][170][171][172][173][174][175][176]. Let us also finally mention another recent review on the Schwinger mechanism more focused on the backreaction and applications in astrophysics [177], as well as some works on the closely related question of pair creation in a curved space-time [178][179][180][181][182][183].…”

Arrows of time and the beginning of the universe

“…(In flat spacetime, this analogy has been recently explored in Refs. [31,32].) At τ > 0, once a pair is created, the positively and negatively charged particles are driven by the electric field in opposite directions, resulting in a nonzero expectation value of the electric current j µ .…”

Entanglement entropy of α-vacua in de Sitter space

“…In the case of pair creation, electron-positron pairs are spontaneously created with a certain separation and such particle states should then be quantum correlated. Recent studies of the Schwinger effect infer that observer frames will be strongly correlated to each other when they observe the nucleation frame [4][5][6].…”