Saturday, September 6, 2014

cosmology - How likely are Primordial Black Holes to form in the early universe?


In the very early universe, tiny fluctuations created slight over- and under-densities in mass/energy. As far as I understand, if a region becomes sufficiently over-dense, a primordial black hole (PBH) would form. This might be very very unlikely, but it should have some non-zero probability everywhere in space.


So my question is:


A) Do we have any sense of how many of these PBHs to expect?


B) The power spectrum was essentially flat back then, which I believe means that the size of fluctuations were scale-invariant (the average over-densities on one scale are twice as big as those at half the scale). Does this mean that PBHs are equally likely to form of any size ??


C) Does inflation have anything to say about this?




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