Production of massive spin — 1/2 particles in Robertson-Walker universes with external electromagnetic fields
In this paper we investigate the combined influence of both cosmological and electromagnetic particle creation mechanisms upon massive particles with spin 1/2 on the basis of general covariant Dirac theory.
Curved space-time, a radiation-dominated Friedmann universe, is treated as an unquantized gravitational field and the low-frequency part of the 2.7 K background radiation is approximated by homogeneous, constant, and parallel external electric and magnetic fields. We calculate the number density of spin 1/2 particles with massm which are created under the influence of both these external fields.
We find that the electric field and the magnetic field both amplify the genuine, purely gravitational particle production. This influence of the magnetic field, which is in contrast to its reducing effect as far as the creation of spin-zero particles is concerned, can clearly be traced back to its coupling to the spin of the particles.
Under certain conditions the electromagnetic fields in the early universe can influence the particle creation process even more than the gravitational field.
KeywordsMagnetic Field Electromagnetic Field Gravitational Field Early Universe Creation Process
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