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LCDM and rotation of DM



 
 
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  #21  
Old August 27th 14, 07:52 AM posted to sci.astro.research
Phillip Helbig---undress to reply
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Posts: 629
Default LCDM and rotation of DM

In article , Nicolaas Vroom
writes:

Not much non-baryonic matter is needed to explain galaxy rotation.

Does that mean that only a small percentage of the total
mass of a galaxy is non-baryonic ?


I think Steve meant "not much" as compared to the total amount of
non-baryonic matter.

The general argument is that if we cannot observe it (being visible)
than it should be non-baryonic.


Not really. About half of the baryons have been unaccounted for.
Recently there is evidence the "missing baryons" are in very hot
intra-cluster gas, but I don't know whether that's yet confirmed.


Which seems to indicate that the necessity for non-baryonic seems
to decrease.


Not necessarily. From big-bang nucleosynthesis, we no the baryon
density. From various cosmological tests, we know the total density.
The difference is non-baryonic.

100% correct and seems to most logical explanation (part of).
This immediatly implies that there also could be much more baryonic
matter outside (but part of) the disk.


You can't exceed the nucleosynthesis constraint, though.

IMO, both, based on observations indicate a missing mass issue
which could be either baryonic or non-baryonic.


You can't exceed the nucleosynthesis constraint, though.

Nowadays there is far more evidence than either of these.


The CMB radiation fluctuations seem to indicate that roughly 20% of all
the mass in the present day is baryonic and 80% is non-baryonic.
The detailed reasoning how these numbers are derived is not
clear to me.


It is well documented. You could read the CMBFAST or CAMB code, or the
papers describing them and references therein, or any of the vast number
of theoretical papers describing how the power spectrum (from which the
conclusions you mentioned) is derived. It's not easy; it's not
necessarily intuitive, but it is straightforward physics with no fudge
factors.

Specific if this balance all ready existed immediate
after the BB and stayed constant there after untill present.


Not immediately after the big bang, but after nucleosynthesis.
  #22  
Old August 27th 14, 03:50 PM posted to sci.astro.research
Richard D. Saam
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Posts: 240
Default LCDM and rotation of DM

On 8/27/14, 1:52 AM, Phillip Helbig---undress to reply wrote:
In article , Nicolaas Vroom
writes:


Which seems to indicate that the necessity for non-baryonic seems
to decrease.


Not necessarily. From big-bang nucleosynthesis, we no the baryon
density. From various cosmological tests, we know the total density.
The difference is non-baryonic.

Big Bang baryon nucleosynthesis calculations
are based on theoretical models developed
during the Manhattan Project and follow-on efforts.
These models were used to define nuclear reactions
at the National Ignition Facility
https://lasers.llnl.gov/
such that there was confidence for 'over unity' energy creation.
This did not happen.
I would not be 100% confident that the same models
are accurate in expressing nuclear dynamics
at the much more complex first minutes of the Big Bang.
  #23  
Old August 28th 14, 09:07 AM posted to sci.astro.research
Phillip Helbig---undress to reply
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Posts: 629
Default LCDM and rotation of DM

In article , "Richard D. Saam"
writes:

Big Bang baryon nucleosynthesis calculations
are based on theoretical models developed
during the Manhattan Project and follow-on efforts.
These models were used to define nuclear reactions
at the National Ignition Facility
https://lasers.llnl.gov/
such that there was confidence for 'over unity' energy creation.
This did not happen.


Reference, please.

I would not be 100% confident that the same models
are accurate in expressing nuclear dynamics
at the much more complex first minutes of the Big Bang.


A large part of the literature on BBN is concerned with refining the
"laboratory values". Even if early estimates were based on sources
which, for whatever reason, were not completely correct, these days are
long since gone.
  #24  
Old August 31st 14, 07:28 PM posted to sci.astro.research
Richard D. Saam
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Posts: 240
Default LCDM and rotation of DM

On 8/28/14, 3:07 AM, Phillip Helbig---undress to reply wrote:
In article , "Richard D. Saam"
writes:

Big Bang baryon nucleosynthesis calculations
are based on theoretical models developed
during the Manhattan Project and follow-on efforts.
These models were used to define nuclear reactions
at the National Ignition Facility
https://lasers.llnl.gov/
such that there was confidence for 'over unity' energy creation.
This did not happen.


Reference, please.

NIF did achieve break even 'over unity' in February, 2014
http://newenergyandfuel.com/http:/ne...ion-breakeven/

with reference to Nature article
http://www.nature.com/nature/journal...ture13008.html

"The experimental results have matched computer simulations much better
than previous experiments, providing an important benchmark for the
models used to predict the behavior of matter under conditions similar
to those generated during a nuclear explosion, a primary goal for the NIF."

but the science continues:
“There is more work to do and physics problems that need to be addressed
before we get to the end, but our team is working to address all the
challenges, and that’s what a scientific team thrives on."


I would not be 100% confident that the same models
are accurate in expressing nuclear dynamics
at the much more complex first minutes of the Big Bang.


A large part of the literature on BBN is concerned with refining the
"laboratory values". Even if early estimates were based on sources
which, for whatever reason, were not completely correct, these days are
long since gone.

But the science continues:
Hints of Mysterious Particle Detected in 'Big Bang Soup'
http://www.livescience.com/47506-hea...ons-found.html
Big Bang Soup conditions were experimentally studied at
7.2 trillion degrees Fahrenheit (4 trillion degrees Kelvin)
This temperature conforms to a radiation dominated universe
at 1.02E-08 sec.
References are made to analogous chemical phase relationships
in explaining the Big Bang Soup.

"Now, the team is hoping to create a map of how different types of
matter, such as quark-gluon plasma, change phases at different
temperatures. Just as the chemical symbol H20 represents water in the
form of a liquid, ice or steam depending on the temperature and
pressure, the subatomic particles in an atom's nucleus take different
forms at different temperatures. So, the team is hoping the new results
could help them to create a map of how nuclear matter behaves at
different temperatures."

These physical chemistry references to
liquid, solid and gas phases
and salting out effect
are not addressed in the standard model.
Further physical chemistry logic
anticipates the existence of critical points between phases
and then there is the Bose Einstein Condensate phase.
And then: how is gravity addressed?

"Refining Laboratory Values" to BBN theory is a continuing process
and will add to understanding the BBN contribution
to the present understanding of
galactic formation, dark matter and dark energy
and in particular the baryonic and non baryonic content in the universe.

Richard D Saam
  #25  
Old September 5th 14, 03:47 PM posted to sci.astro.research
Steve Willner
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Posts: 1,172
Default LCDM and rotation of DM

In article ,
Nicolaas Vroom writes:
Does that mean that only a small percentage of the total
mass of a galaxy is non-baryonic ?


This is hard to study, and it probably varies by galaxy type and
mass. A good guess is perhaps half and half.

The early history of dark-matter is explained in this
document: http://arxiv.org/pdf/astroph/9904251.pdf 1999.


Looks like a nice historical article.

What you need is an excel spreadsheet showing based on 2014
information for all the galaxies of the coma cluster what the
baryonic masses are of each and what the total is,


Yes, that's the sort of approach needed, though there's nothing magic
about Coma. The complication is that measuring the galaxies is not
enough. Intra-cluster gas probably makes up half or more of the
baryonic mass but is very hard to measure.

Total mass can come from velocity dispersions or gravitational
lensing. There's some uncertainty converting velocity dispersion to
mass because it depends on how velocities are distributed.

There is a vast literature on all these questions.

The document shows a sigma value of 706 +- 267 km/sec2
which implies that the total mass has a large uncertainty range.


I'm not sure what document you refer to, but I'd expect a much better
value to be known now.

See also http://arxiv.org/pdf/1110.2649v1.pdf (2011)
which gives a very mixed picture.


That's for the ratio in individual dwarf galaxies. The problem is
similar, but the region being studied differs.

Not really. About half of the baryons have been unaccounted for.
Recently there is evidence the "missing baryons" are in very hot
intra-cluster gas, but I don't know whether that's yet confirmed.


Which seems to indicate that the necessity for non-baryonic seems
to decrease.


No. The total baryon density is known from the CMB, nucleosynthesis,
and I think from baryon acoustic oscillations. Or does that last not
give a density? The question is where those baryons reside. No
matter where they are, there just aren't enough of them to explain
cluster velocity dispersions. And some of the peaks in the CMB
fluctuation power spectrum cannot be explained by baryons at any
density.

The CMB radiation fluctuations seem to indicate that roughly 20% of all
the mass in the present day is baryonic and 80% is non-baryonic.
The detailed reasoning how these numbers are derived is not
clear to me.


It's far from obvious! Try playing with the simulator at
http://lambda.gsfc.nasa.gov/education/cmb_plotter/
and look at the related documentation. The "lambda" site has huge
amounts of information.

Specific if this balance all ready existed immediate
after the BB and stayed constant there after untill present.


Current theory says the amounts of baryonic and non-baryonic matter
have stayed fixed at all times since the Universe became matter
dominated.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
  #26  
Old September 7th 14, 10:02 AM posted to sci.astro.research
Phillip Helbig---undress to reply
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Posts: 629
Default LCDM and rotation of DM

In article , Steve Willner
writes:

Current theory says the amounts of baryonic and non-baryonic matter
have stayed fixed at all times since the Universe became matter
dominated.


Right. There are actually quite strong limits on this, as some theories
predicted proton decay (which would violate baryon-number conservation)
and people have looked for it. They didn't find it. This rules out
those theories and also indicates that the ratio hasn't changed. (Of
course, one cannot rule out that it has change via some other mechanism,
but there is absolutely no evidence for this observationally, and no
reason to expect it theoretically.)
  #27  
Old September 7th 14, 12:15 PM posted to sci.astro.research
Jos Bergervoet
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Posts: 126
Default LCDM and rotation of DM

On 9/7/2014 11:02 AM, Phillip Helbig---undress to reply wrote:
In , Steve Willner
writes:

Current theory says the amounts of baryonic and non-baryonic matter
have stayed fixed at all times since the Universe became matter
dominated.


Right. There are actually quite strong limits on this, as some theories
predicted proton decay (which would violate baryon-number conservation)
and people have looked for it. They didn't find it. This rules out
those theories and also indicates that the ratio hasn't changed.


For the *ratio* to be unchanged you also would need
to rule out decay of the other component. At the
moment we are not yet in the era of "precision
dark matter theories" (although it will come, of
course!) but suppose, for the sake of argument,
and also because I find it convenient, that it
consists of axions (the dark matter, I mean) then
our current theory certainly does predict certain
decay modes.

In fact, physicists are actively trying to induce
those decays right now:
http://www.phys.washington.edu/groups/admx/home.html

(Of course, one cannot rule out that it has change via some other mechanism,
but there is absolutely no evidence for this observationally, and no
reason to expect it theoretically.)


But axions do decay (or get created) in a magnetic
field! So theoretically at least it is possible. (I
admit that observationally you may have a point, or
else the headlines would be all over the planet by
now, I'm sure..)

--
Jos
  #28  
Old September 8th 14, 09:11 AM posted to sci.astro.research
Richard D. Saam
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Posts: 240
Default LCDM and rotation of DM

On 9/7/14, 4:02 AM, Phillip Helbig---undress to reply wrote:
In article , Steve Willner
writes:

Current theory says the amounts of baryonic and non-baryonic matter
have stayed fixed at all times since the Universe became matter
dominated.


Right. There are actually quite strong limits on this, as some theories
predicted proton decay (which would violate baryon-number conservation)
and people have looked for it. They didn't find it. This rules out
those theories and also indicates that the ratio hasn't changed. (Of
course, one cannot rule out that it has change via some other mechanism,
but there is absolutely no evidence for this observationally, and no
reason to expect it theoretically.)

Ref: First Direct Measurement of the H2Li6 Cross Section
at Big Bang Energies and the Primordial Lithium Problem
http://physicsworld.com/cws/article/...n-of-lithium-6

Such studies continue to confirm
the accepted baryonic and non-baryonic ratio.

But this experiment with hydrogen nuclei (atomic weight 1)
does not study the colligative properties of primordial nucleosynthesis
such as when much higher nuclei number are present,
expressed in gold (atomic weight 196.97) atom collisions
simulating the near infinity
Big Bang nucleosynthetic(BBN) atomic weight:

Hints of Mysterious Particle Detected in 'Big Bang Soup'
http://www.livescience.com/47506-hea...ons-found.html

These BBN colligative properties may provide a reason to expect
a different baryonic and non-baryonic ratio.
  #29  
Old September 8th 14, 09:12 AM posted to sci.astro.research
Phillip Helbig---undress to reply
external usenet poster
 
Posts: 629
Default LCDM and rotation of DM

In article , Jos Bergervoet
writes:

For the *ratio* to be unchanged you also would need
to rule out decay of the other component.


Right, of course.

At the
moment we are not yet in the era of "precision
dark matter theories" (although it will come, of
course!) but suppose, for the sake of argument,
and also because I find it convenient, that it
consists of axions (the dark matter, I mean) then
our current theory certainly does predict certain
decay modes.


Of course, if it decays to some other non-baryonic particle, then the
ratio stays the same. If it decays completely to radiation (or to
something baryonic) then, yes, the ratio would change.

However, if the ratio substantially changed with time, then this would
probably contradict some observation the interpretation of which assumes
a constant ratio.
 




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