Relativistic EPC in Intergalactic Medium

The development of electromagnetic cascades in photon gas and magnetic fields is a rather common phenomenon in astrophysics. In photon fields such cascades can be created on almost all astronomical scales, from compact objects like accreting black holes, fireballs in gamma-ray bursts, sub-pc jets of blazars to large-scale (up to 100 kpc) AGN jets and 1 Mpc size clusters of galaxies. Since the energy density of 2.7 \(^\circ \) K CMBR significantly exceeds it of intergalactic magnetic fields, these interactions initiate electron–photon cascades. The contributions of \(\gamma \) -rays from these cascades should constitute a noticeable fraction into the diffuse extragalactic background.