Schwinger effect in de Sitter space

Abstract

We consider Schwinger pair production in 1+1 dimensional de Sitter space, filled with a constant electric field E. This can be thought of as a model for describing false vacuum decay beyond the semiclassical approximation, where pairs of a quantum field ϕ of mass m and charge e play the role of vacuum bubbles. We find that the adiabatic ``in" vacuum associated with the flat chart develops a space-like expectation value for the current J, which manifestly breaks the de Sitter invariance of the background fields. We derive a simple expression for J(E), showing that both ``upward" and ``downward" tunneling contribute to the build-up of the current. For heavy fields, with m2 ≫ eE,H2, the current is exponentially suppressed, in agreement with the results of semiclassical instanton methods. Here, H is the inverse de Sitter radius. On the other hand, light fields with m ≪ H lead to a phenomenon of infrared hyperconductivity, where a very small electric field mH≲eE ≪ H2 leads to a very large current J ∼ H3/E. We also show that all Hadamard states for ϕ necessarily break de Sitter invariance. Finally, we comment on the role of initial conditions, and ``persistence of memory" effects.

Schwinger effect in 4D de Sitter space and constraints on magnetogenesis in the early universe

“…However, unlike in the two-dimensional case [7] where the current under weak electric fields is exponentially suppressed for massive scalars, in four-dimensions the scaling (1.2) holds for arbitrary masses. Therefore charged massive scalars can also give rise to non-negligible conductivity in a dS universe under weak electric fields.…”

“…is to study the expectation value of the induced current, as in [7,[9][10][11][12][13][14]. This allows us to analyze cases where even the adiabatic vacuum does not exist in the asymptotic future, in other words, regimes where the scalar mass and electric force are much smaller than the Hubble scale and thus the scalar excitations are not well described as particles.…”

“…Such a semiclassical approach provides good approximations in some parameter regions (as we will see later), but not in general. In particular, computing the contribution only from the created particles is not enough, as such a naive picture violates local charge conservation [7]. Moreover, the analyses in the previous subsection were limited to cases where the mass and/or the electric force are sufficiently larger than the Hubble scale, cf.…”

“…The possibility of electromagnetic fields existing in the early universe motivates us to look into effects induced by electromagnetic fields in curved spacetimes. Recently, the Schwinger effect in two-dimensional de Sitter (dS) space was studied in [7] (see also [8]). The authors found behaviors quite different from those in flat space; for instance, a large current is induced under weak electric fields, when the mass of the charged particle is much smaller than the Hubble scale, a phenomenon dubbed as "hyperconductivity".…”

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].…”