Can pregalactic black holes produce the hard X-ray background

The possibility that pregalactic black hole accretion could have heated the Universe sufficiently to produce the hard X-ray background through bremsstrahlung emission is considered. This would only be possible if the holes were implausibly large. However, the radiation produced directly from the accretion could explain both the density and spectrum of the X-ray background providing that the holes had a density of the order of 10-6 times the critical density and a mass of the order of 109 Solar Masses. It is suggested that these holes could be the precursors of the holes which may presently be powering Seyfert galaxies or quasars. (author)