We study exact solutions of Dirac and Klein–Gordon equations and Green functions in d-dimensional QED and in an external electromagnetic field with constant and homogeneous field invariants. The cases of even and odd dimensions are considered separately; they are essentially different. We direct attention to the asymmetry of the quasienergy spectrum, which appears in odd dimensions. The in and out classification of the exact solutions as well as the completeness and orthogonality relations is strictly proven. Different Green functions in the form of sums over the exact solutions are constructed. The Fock–Schwinger proper time integral representations of these Green functions are found. As physical applications, we consider the calculations of different quantum effects related to the vacuum instability in the external field. For example, we present mean values of particles created from the vacuum, the probability of the vacuum remaining a vacuum, the effective action, and the expectation values of the curr...

QED in external field with space–time uniform invariants: Exact solutions

The influence of electromagnetic fields on the creation of scalar particles from vacuum in a flat Robertson–Walker space-time is studied. The Klein–Gordon equation with varying electric field and constant magnetic one is solved. The Bogoliubov transformation method is applied to calculate the pair creation probability and the number density of created particles. It is shown that the electric field amplifies the creation of scalar particles while the magnetic field minimizes it.

Effect of electromagnetic fields on the creation of scalar particles in a flat Robertson–Walker space-time

Creation of vector bosons by an electric field in curved spacetime

On the scalar particle creation by electromagnetic fields in Robertson–Walker spacetime

The problem of particle creation from vacuum in a flat Robertson-Walker space-time in the presence of a varying electric field is studied. The Klein Gordon equation is exactly solved when the scale factor is a(η)=A+Btanh(λη). The canonical method based on Bogoliubov transformation is applied. The pair creation probability and the density number of created particles are calculated. The particular case of radiation dominated universe is considered where the total probability is written as a Schwinger-like series. It is shown that the electric field amplifies gravitational particle creation.

Schwinger Effect in a Robertson-Walker Space-Time

The amount of particle pairs created in a 3-flat Robertson-Walker Universe with an expansion law for the early Universe is calculated exactly when a homogeneous electromagnetic field is present. Under some restrictions a time-dependent particle creation rate is found. Finally it is shown that the low-frequency part of the cosmological 2.7K background radiation can be identified with the stationary electromagnetic field discussed before. According to this a large amount of particles of the order of the number of particles in the Universe should be created out of the vacuum in the immediate neighbourhood of the 'big bang'.

http://iopscience.iop.org/article/10.1088/0305-4470/13/2/019/pdf

H Dehnen

Papers

Pair creation in cosmology when electromagnetic fields are present