Primordial black holes ruled out as dark matter candidate

[Chronos]

Primordial black holes as a dark matter candidate has been ruled out - http://www.nature.com/news/search-for-primordial-black-holes-called-off-1.14551

 

[mfb]

Well, there is a hole at [2 to 4]*10^24g (see figure 2 in the preprint - a few % of the mass of our moon), but that would require some mechanism to produce many black holes of this size without other sizes.

A nice method with a nice result. Good, I didn't like that idea anyway.

 

[Haelfix]

There is some uncertainty in the theoretical description that the paper is referring too and in principle there could remain a small window there. A far greater problem for primordial black holes, and one that has plagued them since the start is that they have been constrained by the far more robust Microlensing experiments and other Macho searches to an already very tiny window.

Would nature be so perverse to squeeze an enormous amount of them in right there, just coincidentally in the spot where human's can't see? Especially since we have absolutely no plausible explanation for their theoretical formation in the early universe.

 

[Chronos]

It does seem any mechanism that would slot PBH mass to some specific mass range would be exotic. I still suspect far more massive PBH's are responsible for supermassive black holes. There are plenty of other candidate explanations for DM, but, it is difficult to imagine rational alternatives for SMBH's at high z.

 

[marcus]

Is any of this considered to be evidence that PBH do not exist?

I thought it was ruled out merely that PBH are not abundant enough to be considered as a substantial part of Dark Matter. There are other ideas about dark matter (sterile neutrinos around 7 kev, etc etc).

So we don't have to worry about there being a LOT of PBH, and it seems to me that the mechanism by which some PBH could have formed are still reasonable. Or?

Would it be correct to interpret "primordial black holes ruled out" as a grossly misleading headline, since their existence, as far as we know, has not been ruled out?

Should I not be skeptical when I hear about PBH being "ruled out"? Puzzled.

 

[Haelfix]

This is about their use as an explanation for dark matter.

Is it possible there is a single PBH somewhere within our Hubble sphere? Yes, although part of the problem is we simply don't have any concrete/precise model for how they form in the early universe from first principles. We don't know anything about their cross section, or what sort of mass spectrum they output from generic conditions.

These sorts of exotic objects involve extremely difficult numerical calculations of turbulent (hydrodynamics) GR collapse models and despite being studied for decades, the state of the art requires a lot of sensitive tuning within the initial conditions as well as pretty uncontrolled adhoc approximations and ansatz's...

 

[marcus]

Is it possible there is a single PBH somewhere within our Hubble sphere? Yes,...

So they are not ruled out. So the headline must be, as I suspected, grossly misleading. The headline does not say anything about PBH as constituent of dark matter. PBH per se have not been ruled out.

Obviously if there could be one, there could be a million PBH within our Hubble sphere. We simply do not know enough to rule that out.
And one way to search for them would be to check for apparently isotropic very short gamma ray bursts. Or more precisely for GRB which are not easily explained by the usual models.

So there are professional researchers interested in the statistics and the directional distribution of very short GRB, with the explicit assumption that one possible explanation of this distinctive type of GRB might be that they result from the end-of-life flash of PBH.

One of the astrophysicists involved is Cline. I'll get a paper to illustrate.

 

[marcus]

http://arxiv.org/find/grp_physics/1/AND+au:+cline_d+ti:+primordial/0/1/0/all/0/1
1. arXiv:1105.5363 [pdf]
Do Very Short Gamma Ray Bursts originate from Primordial Black Holes? Review
David B. Cline, Stan Otwinowski, Bozena Czerny, Agnieszka Janiuk
Comments: 12 pages, 10 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

2. arXiv:0908.1352 [pdf]
Evidence for Primordial Black Hole Final Evaporation: Swift, BATSE and KONUS and Comparisons of VSGRBs and Observations of VSB That Have PBH Time Signatures
David B. Cline, Stan Otwinowski
Comments: 11 pages, 7 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

3. arXiv:0704.2398 [pdf]
The Search for Primordial Black Holes Using Very Short Gamma Ray Bursts
D.B. Cline, C. Matthey, S. Otwinowski, B. Czerny, A. Janiuk
Comments: 5 pages, 3 figures, talk given at the "Outstanding Questions for the Standard Cosmological Model" meeting, Imperial College, UK, March 2007
Subjects: Astrophysics (astro-ph)

4. arXiv:astro-ph/0110276 [pdf]
Evidence for a Galactic Origin of Very Short Gamma Ray Bursts and Primordial Black Hole Sources
D.B. Cline, C. Matthey, S. Otwinowski
Comments: 10 pages, 4 figures
Journal-ref: Astropart.Phys. 18 (2003) 531-538
Subjects: Astrophysics (astro-ph)

5. arXiv:astro-ph/0103137 [pdf, ps]
Primordial Black Holes and the Asymmetrical Distribution of Short GRB Events
David B. Cline
Subjects: Astrophysics (astro-ph)

http://inspirehep.net/author/profile/D.Cline.1
David Bruce Cline, over 44,000 lifetime citations
over 700 published papers to which on average of 61 citations per paper.

In sum, it's obviously legit to look for evidence of PBH in certain types of GRB events, and smart reputable people do it.
Nothing that has come up, referred to in this thread (or elsewhere as far as I know) has ruled out the existence of PBH. So how about we make that clear?

 

[marcus]

Here's a recent review of PBH research to be included as chapter of forthcoming book on quantum aspects of black holes to be published by Springer Press edited by Xavier Calmet (btw, a former PF poster!)

http://arxiv.org/abs/1403.1198
Primordial Black Holes: sirens of the early Universe
Anne M. Green
(Submitted on 5 Mar 2014)
Primordial Black Holes (PBHs) are, typically light, black holes which can form in the early Universe. There are a number of formation mechanisms, including the collapse of large density perturbations, cosmic string loops and bubble collisions. The number of PBHs formed is tightly constrained by the consequences of their evaporation and their lensing and dynamical effects. Therefore PBHs are a powerful probe of the physics of the early Universe, in particular models of inflation. They are also a potential cold dark matter candidate.
21 pages. To be published in "Quantum Aspects of Black Holes", ed. X. Calmet (Springer, 2014)

 

[Chronos]

... In sum, it's obviously legit to look for evidence of PBH in certain types of GRB events, and smart reputable people do it. Nothing that has come up, referred to in this thread (or elsewhere as far as I know) has ruled out the existence of PBH. So how about we make that clear?

Fair enough, the Nature article was not unclear about this. The thread title, not so much. I accept the flogging.

 

[marcus]

Chronos, please consider yourself UNflogged Your post made it explicitly clear: ruled out as dark matter.
The title just needed those three extra words. A mentor could have remedied the omission ere now.

But what you actually found a pointer to is something really interesting. (You've been spotting great stuff recently! I benefit a lot--it's like having an extra pair of eyes, or ESP.) So thanks.

What you pointed us to, of course, is:
http://arxiv.org/abs/1401.3025
Exclusion of the remaining mass window for primordial black holes as the dominant constituent of dark matter
by Abraham Loeb and Paolo Pani

It has a fascinating explanation of how a BH with mass between 10¹⁴ and 10²¹ kg , if it ever encountered a neutron star, would eventually pass right through (because so tiny), but could be captured by the star (by tidal dissipation of energy), and then would begin to eat the star from within, and disrupt it.

So if there were a LOT of those BH all over the place that would spell disaster for neutron stars.

So there can't be a LOT. (But probably most of us already had reckoned there weren't scads of PBH around. What interests me is that there might be enough to explain a certain class of observed gamma bursts.)

To me the interesting thing about this Loeb and Pani paper is their describing a mechanism by which a BH could be captured, in the unlikely event that one randomly collided with a neutron. star.

I respect Avi Loeb , you possibly do so as well. It's a good find. Tomorrow or Monday, the next time I update the bibliography, I'll add this one to it, partly because of its significance in solving the DM puzzle, but also just general interest.

 

[Chronos]

Agreed. The redshift of GRB's suggest they were more common in the early universe. That is consistent with the idea PBH's were more common in the early universe. The idea of PBH/neutron star mergers as an explanation for certain GRB's is therefore logical. I also favor the idea you need PBH's to explain supermassive BH's in the early universe. Permit me to add you are responsible for my obsession with new cosmology papers. I have a litany of topics that attract my interest.