There is still a window of mass for which primordial black hole dark matter has not been ruled out by astronomy observation, although even if there are primordial black holes in the asteroid-mass size range, this still doesn't explain how these produce the halo distributions that are inferred that most popular variants of cold dark matter have been designed to address, so this is still probably a dead end.
Revisiting constraints on asteroid-mass primordial black holes as dark matter candidates
(Submitted on 13 Jun 2019)
As the only dark matter candidate that does not invoke a new particle that survives to the present day, primordial black holes (PBHs) have drawn increasing attention recently. Up to now, various observations have strongly constrained most of the mass range for PBHs, leaving only small windows where PBHs could make up a substantial fraction of the dark matter. Here we revisit the PBH constraints for the asteroid-mass window, i.e., the mass range3.5×10−17M⊙<mPBH<4×10−12M⊙ . We revisit 3 categories of constraints. (1) For optical microlensing, we analyze the finite source size and diffractive effects and discuss the scaling relations between the event rate,mPBH and the event duration. We argue that it will be difficult to push the existing optical microlensing constraints to much lower mPBH . (2) For dynamical capture of PBHs in stars, we derive a general result on the capture rate based on phase space arguments. We argue that survival of stars does not constrain PBHs, but that disruption of stars by captured PBHs should occur and that the asteroid-mass PBH hypothesis could be constrained if we can work out the observational signature of this process. (3) For destruction of white dwarfs by PBHs that pass through the white dwarf without getting gravitationally captured, but which produce a shock that ignites carbon fusion, we perform a 1+1D hydrodynamic simulation to explore the post-shock temperature and relevant timescales, and again we find this constraint to be ineffective. In summary, we find that the asteroid-mass window remains open for PBHs to account for all the dark matter.
Submission history
From: Paulo Montero-Camacho [view email][v1] Thu, 13 Jun 2019 22:20:18 UTC (1,058 KB)
5 comments:
"even if there are primordial black holes in the asteroid-mass size range, this still doesn't explain how these produce the halo distributions that are inferred that most popular variants of cold dark matter have been designed to address, so this is still probably a dead end."
perhaps not by itself but if you combine it with MOND
do you know if asteroid-mass primordial black holes can also explain the third peak of the CMB?
If you combine it with MOND you only need PBHs in clusters but have to explain why they are only in clusters. Or you have come up with a modified gravity theory different from MOND that solves the cluster mass shortfall as well and other MOND issues.
I don't know if PBHs can explain the third peak of the CMB. Dark matter needs to be nearly collisionless in LambdaCDM, which PBH dark matter is not.
"f you combine it with MOND you only need PBHs in clusters but have to explain why they are only in clusters."
maybe PBH are so thinly spread out that their aggregate mass only shows up in cluster scales in combination with MOND
even stacy mcgaugh acknowledges the third peak of the CMB simplest explanation is dark matter.
perhaps MOND + sterile neutrinos + PBH
FWIW, I think that both sterile neutrinos and PBH are both very unlikely, even though they aren't quite definitively and completely ruled out.
I strongly suspect that there are some gravitational modification which reproduce the CMB third peak because the same properties that make the gravitational modification look like a DM halo in galaxies could also look like DM when incorporated into cosmology models. The trouble is that to really do that right, you need to throw out most of the lambdaCDM model and start over almost from scratch, rather than merely slightly tweaking it (as far as anyone has been able to manage so far).
I have a citation to a paper in some post tagged "dark matter" at this blog that proves that it is possible, at least in principle, to reproduce the CMB peaks in a modified gravity theory approximated by a scalar graviton. I think I may also cite to it in my archive page on Deur's work.
on this blog i recall both conformal gravity and gravity with self-energy both giving rise to MOND.
i wonder how they fare in the third peak of CMB.
gravitational lensing is also evidence of dark matter, ethan siegal discusses this in context of the bullet cluster,
one MOND objection to bullet cluster as cited by sabine hossfelder was the velocities which are higher than CDM simulations, by 1 in a million, but now ethan siegal says magnetic fields can explain the velocity while preserving dark matter
https://www.forbes.com/sites/startswithabang/2019/06/06/scientists-discover-spaces-largest-intergalactic-bridge-solving-a-huge-dark-matter-puzzle/#3b1f5760546b
so perhaps PBH plus MOND is the way to save MOND.
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