This study is pretty much the nail in the coffin of already troubled primordial black hole dark matter models. The key finding is in bold in the abstract below.
[Submitted on 12 May 2020]Primordial Black Holes Confront LIGO/Virgo data: Current situation
The LIGO and Virgo Interferometers have so far provided 11 gravitational-wave (GW) observations of black-hole binaries. Similar detections are bound to become very frequent in the near future. With the current and upcoming wealth of data, it is possible to confront specific formation models with observations. We investigate here whether current data are compatible with the hypothesis that LIGO/Virgo black holes are of primordial origin. We compute in detail the mass and spin distributions of primordial black holes (PBHs), their merger rates, the stochastic background of unresolved coalescences, and confront them with current data from the first two observational runs, also including the recently discovered GW190412. We compute the best-fit values for the parameters of the PBH mass distribution at formation that are compatible with current GW data. In all cases, the maximum fraction of PBHs in dark matter is constrained by these observations to befPBH≈few×10−3 . We discuss the predictions of the PBH scenario that can be directly tested as new data become available. In the most likely formation scenarios where PBHs are born with negligible spin, the fact that at least one of the components of GW190412 is moderately spinning is incompatible with a primordial origin for this event, unless accretion or hierarchical mergers are significant. In the absence of accretion, current non-GW constraints already exclude that LIGO/Virgo events are all of primordial origin, whereas in the presence of accretion the GW bounds on the PBH abundance are the most stringent ones in the relevant mass range. A strong phase of accretion during the cosmic history would favour mass ratios close to unity, and a redshift-dependent correlation between high masses, high spins and nearly-equal mass binaries, with the secondary component spinning faster than the primary.
I don't dispute the conclusion of this paper, but do you think the 2 papers I linked on MOND " is pretty much the nail in the coffin " of MOND and therefore Deur by extension?
ReplyDeletethere are papers that show problems with various dark matter proposals, and papers that seemingly refute MOND
Sabine had a post on the philosophy of MOND, and she argues MOND is in contradiction to GR/Newton, so it's hard to see how Deur can escape these issues.
The MOND expert of that book acknowledges that while MOND can explain the second peak of the CMB, it cannot explain the third peak, and that the third peak remains best explained by dark matter, which can also explain everything MOND purports to explain.
I wonder if MOND claim of ao is wrong, that it is something else going on with gravity or inertia, but not ao which Milgrom has claimed.
'I don't dispute the conclusion of this paper, but do you think the 2 papers I linked on MOND " is pretty much the nail in the coffin " of MOND and therefore Deur by extension?"
ReplyDeleteDefinitely not.
I don't have the time or space in a comment to spell it out the issues with each of those papers here, but one of the articles cited is doing bad statistical analysis, which has been addressed in responses to it.
MOND is a toy model relative to Newtonian physics that isn't supposed to be valid outside its domain of applicability. GR is probably almost perfect in strong fields and, at least as conventionally applied and implemented, materially wrong in very weak fields. So, there should be some contradiction of GR. The weak equivalence principle is probably wrong. Deur's approach, which is a ground up quantum gravity approach (but can also be done classically) focusing on self-interaction of gravitational fields does escape a lot of the technical flaws in MOND that Sabine identifies.
Dark matter predicts nothing in advance, which is a serious flaw. It is an incomplete theory since you need both a particle description and a model to explain how it ends up arranged in the universe for it to be complete and neither has been accomplished. LambdaCDM has multiple fatal flaws. No competitor dark matter theory works yet either. Clearly, there is beyond GR + Standard Model physics at work in dark matter/dark energy observations. But, no dark matter theory adequately explains it.
But, it is reasonable to hope (although it is hard to test explicitly in non-linear models) that any theory which reproduces the galactic scale phenomena attributable to dark matter is also likely to reproduce the cosmology scales attributed to dark matter.
The existence of a universal constant a0 is one respect in which Deur and MOND differ. Deur has no separate a0 constant as a fundamental constant (having only Newton's constant G as fundamental, it also lacks a cosmological constant lambda). But, the shape of a matter distribution plays a role in whether apparent dark matter phenomena kick in. In perfectly spherically symmetric systems there is no effect. The closer you get to a disk-shaped system, the stronger the effect gets. The closer you get to isolated two point source systems you get, it gets even stronger. That is how it can solve the cluster scale difficulties of MOND.