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Did LIGO Detect Dark Matter? - New paper on arxiv.org



 
 
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  #1  
Old March 3rd 16, 07:46 AM posted to sci.astro.research
Robert L. Oldershaw
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Default Did LIGO Detect Dark Matter? - New paper on arxiv.org

http://arxiv.org/abs/1603.00464

Title: Did LIGO detect dark matter?

AUs: Bird et al

Possible evidence for primordial black holes as dark matter.

RLO http://www3.amherst.edu/~rloldershaw
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  #2  
Old March 4th 16, 07:34 AM posted to sci.astro.research
Robert L. Oldershaw
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Default Did LIGO Detect Dark Matter? - New paper on arxiv.org

Also intriguing is the report in yesterday's Nature that some FRB
sources appear to repeat, which apparently means they are single
ultracompact objects rather than mergers.

Also in Science yesterday is a nice article showing cosmic ray
evidence for an unidentified LOCAL population of compact cosmic ray
accelerators.

One is inclined to ask if there is a large but previously unidentified
population of very high energy ultracompact sources that has yet to be
fully discovered and characterized.

RLO http://www3.amherst.edu/~rloldershaw
  #3  
Old March 4th 16, 07:35 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
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Default Did LIGO Detect Dark Matter? - New paper on arxiv.org

In article , "Robert L.
Oldershaw" writes:

http://arxiv.org/abs/1603.00464

Title: Did LIGO detect dark matter?


Almost by definition, black-hole physics is the same no matter what the
black holes are "made of". So, of course, they could be made of dark
matter, or back issues of the ApJ, or whatever.

Possible evidence for primordial black holes as dark matter.


But the paper above is in no way evidence, not even partial evidence,
for primordial black holes as dark matter. It's saying they could be
dark matter, and that black holes in this mass range are not ruled out
(though I think the Lacy & Ostriker argument rules out them being a
substantial fraction of cosmological dark matter).

It seems to me that the paper is jumping on the bandwagon and trying to
get "LIGO" and "dark matter" into one paper. Not wrong, but not really
relevant.
  #4  
Old March 4th 16, 02:28 PM posted to sci.astro.research
Richard D. Saam
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Default Did LIGO Detect Dark Matter? - New paper on arxiv.org

On 3/4/16 1:34 AM, Robert L. Oldershaw wrote:
Also intriguing is the report in yesterday's Nature that some FRB
sources appear to repeat, which apparently means they are single
ultracompact objects rather than mergers.


In your referenced paper:
E. F. Keane, et al.,
The host galaxy of a fast radio burst
Nature doi:10.1038/nature17140
and a quote therein:

"The dispersion measure and redshift, in combination,
provide a direct measurement of the
cosmic density of ionized baryons
in the intergalactic medium of
Omega_IGM = 4.9 +/- 1.3 percent"

It is important to note 4.9 percent refers to ionized baryons
and is not an indicator of non ionized baryons,
if they exist,
outside present Big Bang nucleosynthetic formulations.

RDS

[Mod. note: non-ASCII characters removed. PLEASE DO NOT CUT AND PASTE
FORMULAE FROM PAPERS -- mjh]
  #5  
Old March 5th 16, 09:36 AM posted to sci.astro.research
Robert L. Oldershaw
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Posts: 617
Default Did LIGO Detect Dark Matter? - New paper on arxiv.org

On Friday, March 4, 2016 at 2:36:09 AM UTC-5, Phillip Helbig (undress to reply) wrote:
In article , "Robert L.
Oldershaw" writes:

http://arxiv.org/abs/1603.00464

Title: Did LIGO detect dark matter?


Almost by definition, black-hole physics is the same no matter what the
black holes are "made of". So, of course, they could be made of dark
matter, or back issues of the ApJ, or whatever.


But presumably you are well enough informed to know that the dark
matter is non-baryonic and why that means SN-generated BHs and PBHs
must be distinguished in conventional astrophysics when it comes to
dark matter research

for primordial black holes as dark matter. It's saying they could be
dark matter, and that black holes in this mass range are not ruled out
(though I think the Lacy & Ostriker argument rules out them being a
substantial fraction of cosmological dark matter).


Perhaps you should review that paper, and post a LINK to that paper
(if it is from the arxiv era), and make sure more recent research has
not invalidated their conclusions.


It seems to me that the paper is jumping on the bandwagon and trying to
get "LIGO" and "dark matter" into one paper. Not wrong, but not really
relevant.


Weren't you the one accusing me of making disparaging comments about
the motives of authors. Does Dr. Phil speak with forked tongue?

RLO http://www3.amherst.edu/~rloldershaw
  #6  
Old March 7th 16, 07:58 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
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Posts: 273
Default Did LIGO Detect Dark Matter? - New paper on arxiv.org

In article , "Robert L.
Oldershaw" writes:

http://arxiv.org/abs/1603.00464

Title: Did LIGO detect dark matter?


Almost by definition, black-hole physics is the same no matter what the
black holes are "made of". So, of course, they could be made of dark
matter, or back issues of the ApJ, or whatever.


But presumably you are well enough informed to know that the dark
matter is non-baryonic and why that means SN-generated BHs and PBHs
must be distinguished in conventional astrophysics when it comes to
dark matter research


Yes, but there is no way one can distinguish them in the LIGO data.

for primordial black holes as dark matter. It's saying they could be
dark matter, and that black holes in this mass range are not ruled out
(though I think the Lacy & Ostriker argument rules out them being a
substantial fraction of cosmological dark matter).


Perhaps you should review that paper, and post a LINK to that paper
(if it is from the arxiv era), and make sure more recent research has
not invalidated their conclusions.


It's Lacey, not Lacy; sorry about that. Pre-arXiv. ADS has only one
refereed-journal paper by these two authors (there is also a
conference-proceedings contribution with the same title but without a
question mark). So, go the the ADS abstract search and search for
papers with Lacey AND Ostriker. Then there are links to the full text.

They were thinking about larger-mass black holes, but on the other hand
VLBI has improved as well in the last 30 years. I don't know what the
current limits, but presumably lensing limits can now rule out
lower-mass objects.

It seems to me that the paper is jumping on the bandwagon and trying to
get "LIGO" and "dark matter" into one paper. Not wrong, but not really
relevant.


Weren't you the one accusing me of making disparaging comments about
the motives of authors.


There is a HUGE difference between claiming that someone intentionally
fudged their results to get an answer they wanted to get, and expressing
the opinion that a decision might have been made to write a paper (as I
noted, "not wrong") which contains some topical buzzwords as opposed to
writing some other paper.
  #7  
Old March 7th 16, 09:23 PM posted to sci.astro.research
Robert L. Oldershaw
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Posts: 617
Default Did LIGO Detect Dark Matter? - New paper on arxiv.org

On Monday, March 7, 2016 at 2:58:24 AM UTC-5, Phillip Helbig (undress to reply) wrote:


Yes, but there is no way one can distinguish them in the LIGO data.


The authors of that paper were specifically discussing the fact that
primordial black holes were scientifically valid and interesting
candidates. No more , no less.



It's Lacey, not Lacy; sorry about that. Pre-arXiv. ADS has only one
refereed-journal paper by these two authors (there is also a
conference-proceedings contribution with the same title but without a
question mark). So, go the the ADS abstract search and search for
papers with Lacey AND Ostriker. Then there are links to the full text.

They were thinking about larger-mass black holes, but on the other hand
VLBI has improved as well in the last 30 years. I don't know what the
current limits, but presumably lensing limits can now rule out
lower-mass objects.


So that reference was not the best choice for supportive evidence of
your claims. "Presumes, madam? I know not presumes" (if you know your
Shakespeare).

There is a HUGE difference between claiming that someone intentionally
fudged their results to get an answer they wanted to get, and expressing
the opinion that a decision might have been made to write a paper (as I
noted, "not wrong") which contains some topical buzzwords as opposed to
writing some other paper.


Well, any decent lawyer would have a heyday with your purported
distinction, basing his/her arguments largely on the semantics of the
way you spin things.

Here is a way for objective readers to see this. For years de
Vaucouleurs and Sandage debated fiercely about the value of the Hubble
constant. Using virtually the same data they "proved" that their
favorite value for H was the right one. The problem was that the two
values differed by A FACTOR OF TWO! I respected both astrophysicists.
Today's accepted value is about half-way between. This shows that
one's expectations and preferred answers can play a big role in how
data is analyzed and how tests of ideas are chosen. This is NOT
"INTENTIONALLY FUDGED". It is basic human nature. I was not claiming
that the authors were committing premeditated fraud. I just said they
were perhaps exemplifying the natural human biases discussed above,
and seen over and over again throughout the history of science. It
takes a real effort not to see and understand this.

So it must be taken into account when evaluating theories, models and
opinions.

RLO http://www3.amherst.edu/~rloldershaw
  #8  
Old March 8th 16, 08:17 AM posted to sci.astro.research
Steve Willner
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Posts: 1,172
Default Did LIGO Detect Dark Matter? - New paper on arxiv.org

Nature doi:10.1038/nature17140
"The dispersion measure and redshift, in combination, provide a
direct measurement of the cosmic density of ionized baryons in the
intergalactic medium of Omega_IGM = 4.9 +/- 1.3 percent"


which happens to be exactly the Concordance value for the total
baryon density. The uncertainty is fairly large, though.

In article ,
"Richard D. Saam" writes:
It is important to note 4.9 percent refers to ionized baryons and
is not an indicator of non ionized baryons, if they exist,


Neutral gas would show up in the 21 cm hydrogen line. I don't know
whether this particular line of sight has been observed, but all the
H I masses I know of are far smaller than 4.9%, i.e, neutral gas
seems to be a trivial fraction of the "baryon budget." Stars are a
more significant fraction and (based on the quote above -- I haven't
read the paper yet) are also not accounted for in the ionized gas
measurement.

The interesting thing is that this measurement is in agreement with
newer estimates of ionized gas in galaxy clusters, and the "missing
baryon" problem seems to have gone away.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
  #9  
Old March 8th 16, 03:21 PM posted to sci.astro.research
Jonathan Thornburg [remove -animal to reply][_3_]
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Default systematic errors and the Hubble constant (was: Did LIGO Detect Dark Matter? - New paper on arxiv.org)

Robert L. Oldershaw wrote:
For years de
Vaucouleurs and Sandage debated fiercely about the value of the Hubble
constant. Using virtually the same data they "proved" that their
favorite value for H was the right one. The problem was that the two
values differed by A FACTOR OF TWO!


The key point here is not so much that their values differed a lot,
but that they differed by much more than their claimed error bars
(which were on the order of 15% by the mid-1980s).

It's also important to note that Sandage and de Vaucoulers (and their
many collaborators) did *not* use "virtually the same data". Rather,
they used somewhat different (partially, but not completely, overlapping)
data sets. Due to systematic errors which were not fully understood at
that time, different data sets gave different -- mutually *inconsistent*
-- values for H_0, so one's choice of which data sets to use could change
one's overall mean H_0 estimate by much more than the estimated error
bars.



There's an interesting Bayesian analysis of how to combine mutually
inconsistent measurements, using published Hubble-constant data from
the mid-1990s as a test data set, in

William H Press
"Understanding Data Better with Bayesian and Global Statistical Methods"
astro-ph/9604126
published as a chapter in
"Unsolved Problems in Astrophysics",
Proceedings of Conference held April 1995 in Honor of John Bahcall,
J.P. Ostriker, ed.
(Princeton: Princeton University Press, ISBN 0-691-01606-2),

Press's analysis assigns each H_0 estimate not only a mean and a
variance, but also a probability of being correct, which is inferred
from the consistency (or lack thereof) of different observations. Using
13 published H_0 values available at that time, this analysis leads to
a Bayesian posterior distribution (figure 1 in that preprint) whose 95%
confidence interval is 66 = H_0 = 82 km/s/Mpc, i.e., which does in
fact contain today's more-accurately-known value. The resulting
"probability of being correct" values are shown in figures 2 and 3
of the preprint.

--
-- "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA
"There was of course no way of knowing whether you were being watched
at any given moment. How often, or on what system, the Thought Police
plugged in on any individual wire was guesswork. It was even conceivable
that they watched everybody all the time." -- George Orwell, "1984"
  #10  
Old March 11th 16, 08:09 AM posted to sci.astro.research
Richard D. Saam
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Posts: 240
Default Did LIGO Detect Dark Matter? - New paper on arxiv.org

On 3/8/16 2:17 AM, Steve Willner wrote:
Nature doi:10.1038/nature17140
"The dispersion measure and redshift, in combination, provide a
direct measurement of the cosmic density of ionized baryons in the
intergalactic medium of Omega_IGM = 4.9 +/- 1.3 percent"


which happens to be exactly the Concordance value for the total
baryon density. The uncertainty is fairly large, though.

In article ,
"Richard D. Saam" writes:
It is important to note 4.9 percent refers to ionized baryons and
is not an indicator of non ionized baryons, if they exist,


Neutral gas would show up in the 21 cm hydrogen line. I don't know
whether this particular line of sight has been observed, but all the
H I masses I know of are far smaller than 4.9%, i.e, neutral gas
seems to be a trivial fraction of the "baryon budget."

This assumes neutral hydrogen in gas form.
What if the neutral hydrogen were in aggregate or clumped form?
For example:
let neutral hydrogen gas with density 1x10^-24 g/cm^3
(on the order of galactic density)
be in clumps with 1 g/cm^3 density and 3,000 cm diameter,
then the distance between clumps would be 1x10^6 cm
defining a mean free path of 1x10^25 cm
(much greater than the galactic diameter typically of 1x10^22 cm
and rendering the neutral hydrogen clumps optically undetectable
by Beer's law)
The 21 cm line would not detect these 3,000 cm clumps here on earth.
I do not know of any current analytical procedure
to detect neutral hydrogen in such aggregate or clumped form.
One can argue that such neutral hydrogen aggregates
would have to be extremely cold (2.7K) to form
and the present BBN models "baryon budget" do not allow them
beyond the 4.9% ionized form
but the fact is that current analytical methods
(other than gravitational lensing methods)
cannot detect them if they exist.

Richard D Saam
 




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