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One of the ideas that might solve some of the dark matter problem are the existence of many small black holes. There is evidence, in principle, for the existence of these small black holes via the theory of "primordial black holes". If we find that these black holes are more abundant than the theory predicts (perhaps due to a miscalulation), then they could go further to explaining the missing matter.

If these small black holes are common, and we know that black holes consume matter, then wouldn't a cosmological model have to be updated to include lots of matter being consumed during expansion, say during inflation and shortly thereafter? Has this been accounted for?

Qmechanic
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Ben Sprott
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2 Answers2

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If we are thinking about gravitational mass then a black hole does not "consume" matter. The gravitational mass of the black hole is essentially the same (certainly at large distances) as the gravitational mass of the matter that has fallen into it. So as far as large scale gravitational effects are concerned, there is no "missing matter" here.

gandalf61
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Primordial black holes may account for some or all of dark matter. The "primordial" tag refers to them being created before the epoch of nucleosynthesis.

The reason for that distinction is that there are constraints on the amount of baryonic (and hence by implication, dark) matter from the primordial abundances created during the epoch of nucleosynthesis. Matter that is "consumed" after that by black holes is going to be mostly baryonic matter (since that is the only matter that can readily lose energy and angular momentum and be captured by a black hole).

Baryonic matter that is hidden in black holes isn't a problem. There may well be some. In fact that would help in accounting for the gap between the amount of baryonic matter we know about in terms of stars and gas and that inferred to have been present at the epoch of nucleosynthesis.

ProfRob
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