Are The Black Holes LIGO Detected the Missing Matter of the Universe?

That's a very good article Bob. Sean Carroll is certainly a theorist worth listening to. He has made an intriguing point about the LIGO detection. That is, what is the population of bodies that we may now sample via the GW detectors and hence what might we legitimately expect as the discovery rate of that category of system ( colliding black holes with the quoted mass range ) ? The other great point is that primordial black holes are such a simple consequence of well known physics. We don't need any new stuff for this. Plus the essential requirement of being testable ie. a halo distribution and little if any EM fuss indicating accretion disks etc.

NB : Primordial means really close to the moment of 'infinite' density when relatively small 'knots of spacetime' may form and become these black holes that we detect today. Initially they were randomly distributed and then went with the general Hubble Flow over the aeons but radiated ( ie. GW emission ) causing clusters around much larger masses ie. galaxies. This is rather like an electron emitting light and thus being captured by a nucleus. This would give a straight forward uniform distribution of dark matter around a galaxy ie. an extended halo.

Cheers, Mike.

( edit ) Ooops. My misunderstanding. The paper referred to by Sean Carroll states :

and so the BH's are already bound within some galaxy's halo by now, but then lose energy by their mutual interaction. So the logic now reaches towards attributing the total BH-BH merger detection rate ( to be observed/assessed from now on ) as made up of 'traditional' BH mergers in co-evolving binary systems PLUS these primordial guys which later undergo chance close encounter.