Scalar current of created pairs by Schwinger mechanism in de Sitter spacetime

Abstract

We consider a charged scalar field in a $D$-dimensional de Sitter spacetime and investigate pair creation by a Schwinger mechanism in a constant electric field background. Using a semiclassical approximation the current of the created pairs has been estimated. We find that the semiclassical current of the created pairs in the strong electric field limit responds as E^{D/2}. Going further but restricting to $D=3$ dimensional de Sitter spacetime, the quantum expectation value of the spacelike component of the induced current has been computed in the in-vacuum state by applying an adiabatic subtraction scheme. We find that, in the strong electric field limit, the current responds as E^{3/2}. In the weak electric field limit the current has a linear response in $E$ and an inverse dependence on the mass of the scalar field. In the case of a massless scalar field, the current varies with E^{-1} which leads to a phenomenon of infrared hyperconductivity. A new relation between infrared hyperconductivity, tachyons, and conformality is discussed, and a scheme to avoid an infrared hyperconductivity regime is proposed. In $D$ dimension, we eventually presented some first estimates of the backreaction of the Schwinger pairs to the gravitational field, and we find a decrease of the Hubble constant due to the pair creation.