[tt] NS: Did black hole 'fireworks' light up early cosmos?

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Did black hole 'fireworks' light up early cosmos?
http://space.newscientist.com/article.ns?id=mg19826594.300&print=true
8.6.6
David Shiga

LONG before the first stars were born, something else may have lit
up the darkness - gamma rays from a swarm of microscopic
"primordial" black holes, each weighing no more than a small
asteroid and forged in the violence of the big bang.

Physicists predict that primordial black holes would have spewed out
radiation, including high-energy gamma rays, while shrinking and
becoming even hotter.

Katherine Mack of Princeton University in New Jersey and Daniel
Wesley of Cambridge University think that such gamma rays would have
warmed the soup of hydrogen gas that filled the universe at the
time. Future radio observatories may be able to measure this
temperature signature indirectly. That's because the hydrogen gas
would also have been absorbing some of the radiation left over from
the big bang, which astronomers can observe today. If the gas had
been warmed by the gamma rays, it would have become less able to
absorb this relic radiation - a signature which we may one day see
if highly sensitive observatories are built. This may provide the
first evidence that primordial black holes existed, say the
researchers.

Of course other things could have warmed the hydrogen gas at this
time, such as dark matter particles, which some physicists reckon
would have been decaying and emitting radiation. But if the black
holes were all born with the same mass, as some models predict, they
would all evaporate at the same time, producing a sudden spike in
temperature after a period of steady warming, rather than the
long-term warming expected from dark matter decay.

"The dark ages are such a great time to look for exotic physics
because very little else is happening," says Mack. The pair
presented the idea at the Fifth Harvard-Smithsonian Conference on
Theoretical Astrophysics in Cambridge, Massachusetts.

Avi Loeb of Harvard University says that the existence of primordial
black holes is still speculative. "But nevertheless, it's a
legitimate possibility that one should explore the consequences of,"
he says. Spotting the gamma-ray signature could also confirm that
black holes do evaporate, which has yet to be observed.

Cosmology - Keep up with the latest ideas in our special report.

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Weblinks

Mack and Wesley abstract
http://adsabs.harvard.edu/abs/2008arXiv0805.1531M
Katherine Mack, Princeton University
http://www.astro.princeton.edu/~mack/