Cosmological considerations on the diffuse γ-ray isotropic background

Bignami et al. have recently studied the problem of the origin of the diffuse γ-ray isotropic radiation. They have concluded that within standard cosmology with Λ=0 and p=0, BL Lacertae objects and Seyfert galaxies can account for most of the diffuse radiation if they have not evolved in time. For QSOs, and evolutionary factor (1+z)4 is allowed by the data. From the study of radio data, however, it is known that strong evolutionary effects are expected. The discrepancy cannot be explained by changing the geometry of the universe, i.e., q0