At most of the last few conferences I've been to, including this one,=20
there has been a talk pointing out that primordial black holes could make=20
up most or all of the (unknown, non-baryonic) dark matter. Some mass=20
ranges have not been ruled out, and some which have been have been ruled=20
out only for all objects of the same mass (or nearly so), rather than a=20
more or less broad distribution (which is a more natural expectation). =20 These would be spinless, and that seems consistent with LIGO data. No=20
new physics is needed. Numerical simulations are still not=20
high-resolution enough to distinguish between even massive black holes=20
and particles of much less mass. Perhaps they can explain the=20
small-scale problems in LambdaCDM. I'm not sure why this is often seen=20
as a dark horse, especially since direct-detection experiments have=20
found no sign of other types of dark matter. (At the same time, absence=20
of evidence is not evidence of absence, and the jury is still out. =20
There are also other types of dark matter which such experiments would=20
not detect.)

The speaker was Juan Garcia Bellido. More details can be found at https://arxiv.org/abs/1906.08217 of which he is one of the four authors.
Of course, my recollection of the talk might be imperfect, but I would
hope that the arXiv paper gets the details right.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)