The gamma-ray background : ) 7is it{ a consequence of metagalactic cosmic ray origin. )]

An estimate is made of the gamma -ray spectrum resulting from an extragalactic, evolving source model of cosmic ray origin in the absence of intergalactic gas. The experimental situation does not at present appear to allow definite rejection of this theory, since the calculated spectrum lies between the extreme observational limits. It is possible that such a theory can explain the cosmic ray spectrum, the isotropy of cosmic rays and the diffuse gamma -ray spectrum.