  This thesis investigates the impact of the background magnetic field on
correlations or entanglement between pairs created by the background electric
field in quantum field theoretic systems in the Minkowski, the primordial
inflationary de Sitter and the Rindler spacetimes. These analyses might provide
insight into the relativistic entanglement in the early inflationary universe
scenario, where such background fields might exist due to primordial
fluctuations, and in the near-horizon of non-extremal black holes, which are
often endowed with background electromagnetic fields due to the accretion of
plasma onto them.
