Dark Matter Particle: Top Candidates

[wolram]

http://arxiv.org/pdf/astro-ph/0403064
This is a 2004 paper 34 pages on dark matter, various candidates for
DM are discussed and categorised
anyone have a favorite DM particle?.

 

[Garth]

Thank you for the link to Gondolo’s paper, we have quite a choice as to our favourite particle. I quote from it:

I present some of the most popular candidates for non-baryonic dark matter.
These include neutrinos, axions, neutralinos, WIMPZILLAs, …WIMPs …[solitons (B-balls and Q-balls)], as non-baryonic dark matter.

He continues,

Nothing is known about the nature of the energy component, which goes under the name of dark energy.

He concludes:

Current cosmological data imply the existence of non-baryonic dark matter. We have discussed some of the most popular candidates and shown that none of the candidates known to exist, i.e. the active neutrinos, can be non-baryonic cold dark matter. Hence to explain the nature of cold dark matter we need to invoke hypothetical particles that have not been detected yet.

Quite

But consider; in Gondolo’s paper Figure 1 on page 2 is the well-known concordance Omega m v Omega lambda diagram. The total Omega is thought to be unity because the WMAP data favours a flat universe; this constrains Omega lambda as the total is thought therefore to be unity.

However other models are also conformally flat, such as SCC which is so - even with a total Omega of only one third. If you notice putting Omega m = 0.33, and therefore the equivalent Omega lambda = 0.66, fits quite well too, in fact it is dead centre of the intersection of the CMB and distant supernovae data sets.

Furthermore the Omega baryonic matter in SCC is 0.22, (effective Omega lambda still 0.66), which is the centre of the Galaxy red shift survey data set.

So one way of understanding the different data sets plotted on that diagram is to say the CMB and distant supernovae data indicate cosmological dynamics determined by the total density whereas the galaxy survey data indicate the dynamics of galaxies and clusters within the universe determined by the baryonic matter, dark and luminous, within those clusters.

Just food for thought.

My favourite dark matter particle is the proton, closely followed by the electron and neutron!

Garth

 

[selfAdjoint]

Garth, conformally flat is different from flat!

 

[Garth]

Garth, conformally flat is different from flat!

True, but conformal transformations preserve angles. The CMB data is based on the angular size of anisotropies in the radiation. The conclusions drawn carry through to conformal transformations of the particular GR model.
Garth

 

[meteor]

I vote for the axion, a WIMP whose mass must be in the range 10^-6-10^-3 eV. The axion is in the category of cold dark matter. I used to have preference for hot dark matter (exemple, the neutrino), but WMAP result indicates that the missing matter is most likely cold dark matter
There's a theory that proposes that the axion could act as dark energy as well. Is called Axion Phantom energy
http://arxiv.org/abs/hep-th/0401082

 

[wolram]

http://www.astro.umd.edu/~ssm/mond/
Garth, Meteor, do you have a view on how these particles arrange
themselves with galaxies?
The url is a link to the mond pages, as you know an alternative to DM.
Although i do not subscribe to the theory it is a good one stop reference.

 

[Garth]

http://www.astro.umd.edu/~ssm/mond/
Garth, Meteor, do you have a view on how these particles arrange
themselves with galaxies?
The url is a link to the mond pages, as you know an alternative to DM.
Although i do not subscribe to the theory it is a good one stop reference.

MOND would be more persuasive if the mechanism that produces the anomalous acceleration was known.

SCC predicts the density of the universe is 2/3 baryonic and 1/3 false vacuum energy. Models already run on such a constitution in the past (2/3 CDM, 1/3 HDM) modeled galaxy formation quite nicely
Garth

 

[meteor]

Garth, Meteor, do you have a view on how these particles arrange
themselves with galaxies?

Wolram,
dark matter is postulated to exist throughout all the universe, not only in galaxies, but also in the intergalactic medium. In disk galaxies for example, they exist in the disk but also in a spherical volume around the disk called the halo. The most widely accepted model for dark matter in halos is the famous NFW profile (Navarro, Frenk, White, 1996). It seems that the ratio of dark matter to visible matter varies according what scale of the universe are you examining. See

http://hermes.physics.ox.ac.uk/users/Astrophysics/guides/galaxies/dkmatter.shtml

"Within galaxies the amount of dark matter appears to exceed the amount of visible matter by a factor of 10 to 1 in some cases, and even more than this for a few galaxies. Within galaxy clusters the ratio of dark to visible matter appears to be even larger still and a general result is that the ratio of dark to visible matter appears to increase as one observes on larger scales. On the very largest scales of all (the scale of the observable Universe) visible matter may account for less than 1% of all the matter in the Universe."

 

[malthis]

Dark Dimension

This might go better in String theory, but couldn't dark matter be a fundamental 'particle' that exists in other dimensions? If all particles are vibrations of a fundamental string, then there's nothing that says there can't be particles that vibrate higher than light. But as speed of light is the measure for our space-time, we wouldn't never detect it inside our space-time. It might be curled up in compact dimensions because of it's FLT vibratory nature. Yet its effects might be inferred, such as through gravitational influence.

Hey, it's as good as made-up particles with ultraweak interactions.

 

[meteor]

A conference given a couple of days ago: "The structure of dark matter halos", by Stefan Gottloeber
http://online.itp.ucsb.edu/online/igm04/gottloeber/
you can hear it if you have Realplayer

 

[Nereid]

But consider; in Gondolo’s paper Figure 1 on page 2 is the well-known concordance Omega m v Omega lambda diagram. The total Omega is thought to be unity because the WMAP data favours a flat universe; this constrains Omega lambda as the total is thought therefore to be unity.

However other models are also conformally flat, such as SCC which is so - even with a total Omega of only one third. If you notice putting Omega m = 0.33, and therefore the equivalent Omega lambda = 0.66, fits quite well too, in fact it is dead centre of the intersection of the CMB and distant supernovae data sets.

Furthermore the Omega baryonic matter in SCC is 0.22, (effective Omega lambda still 0.66), which is the centre of the Galaxy red shift survey data set.

So one way of understanding the different data sets plotted on that diagram is to say the CMB and distant supernovae data indicate cosmological dynamics determined by the total density whereas the galaxy survey data indicate the dynamics of galaxies and clusters within the universe determined by the baryonic matter, dark and luminous, within those clusters.

Just food for thought.

My favourite dark matter particle is the proton, closely followed by the electron and neutron!

I keep promising - to myself - to investigate the data on primordial abundances, observational data on low metalicity stars, Lyman forest work, and so on, to get a richer picture of how well these constrain (rule out?) SCC (the 'Indian team's paper' says nothing useful, unless I've been reading the wrong paper).

As we've discussed before, simply substituting baryonic DM for non-baryonic DM in a cosmological model doesn't get you very far ... the distribution of DM is, in some cases, very well known, so an alternative cosmological model still has plenty of good DM data to get its teeth into. For example, does SCC have a hierarchical approach to galaxy formation? In SCC, what sort of DM would comprise the DM in galaxy halos? If it's baryonic matter, why hasn't it been detected yet (e.g. through footprints in the misnamed galactic cosmic rays, in starbursts resulting from galaxy collisions, in microlensing searches, ...)?

A completely different question: other than SCC, what alternative ('non-standard') cosmological models do away with non-baryonic DM? Please, only those with a reasonable degree of concordance with good observational results.

 

[Garth]

I keep promising - to myself - to investigate the data on primordial abundances, observational data on low metalicity stars, Lyman forest work, and so on, to get a richer picture of how well these constrain (rule out?) SCC (the 'Indian team's paper' says nothing useful, unless I've been reading the wrong paper).

Try:
D.Lohiya, A. Batra, S. Mahajan, A. Mukherjee, http://arxiv.org/abs/nucl-th/ 9902022 ;
Phys. Rev. D60, 108301 (2000).

Annu: A. Batra, D. Lohiya, S. Mahajan, A. Mukherjee, Int. J. Mod.
Physics D10, 1 (2001).

Batra, A., Lohiya, D., Mahajan, S., & Mukherjee, A. 2000, Int. J. Mod. Phys., D9,757;

Batra, A., Sethi, M., & Lohiya, D. 1999, Phys. Rev. D., 60, 108301.

G. Steigman http://arxiv.org/abs/astro-ph/9601126 , (1996) is interesting too!

As we've discussed before, simply substituting baryonic DM for non-baryonic DM in a cosmological model doesn't get you very far ... the distribution of DM is, in some cases, very well known, so an alternative cosmological model still has plenty of good DM data to get its teeth into. For example, does SCC have a hierarchical approach to galaxy formation? In SCC, what sort of DM would comprise the DM in galaxy halos? If it's baryonic matter, why hasn't it been detected yet (e.g. through footprints in the misnamed galactic cosmic rays, in starbursts resulting from galaxy collisions, in microlensing searches, ...)?

good questions applicable to both LCDM and SCC models

A completely different question: other than SCC, what alternative ('non-standard') cosmological models do away with non-baryonic DM? Please, only those with a reasonable degree of concordance with good observational results.

MOND?
Garth

 

[Nereid]

Try:
D.Lohiya, A. Batra, S. Mahajan, A. Mukherjee, http://arxiv.org/abs/nucl-th/ 9902022 ;
Phys. Rev. D60, 108301 (2000).

Annu: A. Batra, D. Lohiya, S. Mahajan, A. Mukherjee, Int. J. Mod.
Physics D10, 1 (2001).

Batra, A., Lohiya, D., Mahajan, S., & Mukherjee, A. 2000, Int. J. Mod. Phys., D9,757;

Batra, A., Sethi, M., & Lohiya, D. 1999, Phys. Rev. D., 60, 108301.

G. Steigman http://arxiv.org/abs/astro-ph/9601126 , (1996) is interesting too!

Thanks.

good questions applicable to both LCDM and SCC models

You are, no doubt, aware of the LCDM 'answers'!

MOND?
Garth

Not AFAIK! MOND's domain of applicability is limited; it certainly does not claim to be universal. In fact, being inconsistent with GR, it's hard to imagine how it could be modified to make it applicable.

 

[Garth]

Thanks.You are, no doubt, aware of the LCDM 'answers'!

Yes - to invent Dark Matter and Energy!
I quote again from Gondolo's paper:

I present some of the most popular candidates for non-baryonic dark matter.These include neutrinos, axions, neutralinos, WIMPZILLAs, …WIMPs …[solitons (B-balls and Q-balls)], as non-baryonic dark matter.
............
Nothing is known about the nature of the energy component, which goes under the name of dark energy.
............
Current cosmological data imply the existence of non-baryonic dark matter. We have discussed some of the most popular candidates and shown that none of the candidates known to exist, i.e. the active neutrinos, can be non-baryonic cold dark matter. Hence to explain the nature of cold dark matter we need to invoke hypothetical particles that have not been detected yet.

(Emphasis mine)

Garth

 

[Garth]

A completely different question: other than SCC, what alternative ('non-standard') cosmological models do away with non-baryonic DM? Please, only those with a reasonable degree of concordance with good observational results.

MOND?

Not AFAIK! MOND's domain of applicability is limited; it certainly does not claim to be universal. In fact, being inconsistent with GR, it's hard to imagine how it could be modified to make it applicable.

There was this paper: Stacy McGaugh http://arxiv.org/abs/astro-ph/0312570
"Confrontation of MOND Predictions with WMAP First Year Data"
although that required a heavy neutrino (1eV), which seems to have been ruled out now.
Although I do not advocate MOND myself, I find its lack of identifying a mechanism to explain the anomalous MOND acceleration no more disqualifying that the standard theory's lack of identifying DM particle and DE to explain its dynamics.

Garth

 

[turbo]

There was this paper: Stacy McGaugh http://arxiv.org/abs/astro-ph/0312570
"Confrontation of MOND Predictions with WMAP First Year Data"
although that required a heavy neutrino (1eV), which seems to have been ruled out now.
Although I do not advocate MOND myself, I find its lack of identifying a mechanism to explain the anomalous MOND acceleration no more disqualifying that the standard theory's lack of identifying DM particle and DE to explain its dynamics.

Garth

How true! In this article:

http://www.esa.int/esaCP/SEME3PXO4HD_FeatureWeek_0.html

the authors explain how dark matter aligns itself very closely with the galaxies in the cluster. They propose no mechanism, and there is no observable effect from the dark matter other than the overly-strong lensing. It is perhaps too easy to measure the errors (as evidenced by excess lensing) in the standard model and attribute them to DM, and even make maps of the distribution of this mysterious stuff.

Garth, I know that you prefer baryonic matter as DM, but what kind of baryonic matter could comprise 90-95% of the cluster mass and have NO thermal signature? (Again, IIR, you propose a much smaller percentage of DM - somewhat on the order of 30%, correct?)

I firmly believe that we will find the zero point energy field to be the real player in this regard. Just a tiny difference in infall rates (matter vs anti-matter) could polarize the ZPE EM field in the presence of huge masses, and that polarization should affect the optical properties of space-time. The breaking of this equivalence (matter/antimatter gravitational infall rates) would also provide a mechanism for giving us a matter-dominated universe, in accordance with Smolin's black-hole universe ideas.

The potential energy of the ZPE field is over 120 orders of magnitude too high to account for the cosmological constant, but what if that energy cannot be expressed if the field is randomly oriented? Polarization due to the presence of mass could express some of this energy, even if the infall rates of matter vs antimatter differ by a small amount. Just a thought...

 

[Garth]

Garth, I know that you prefer baryonic matter as DM, but what kind of baryonic matter could comprise 90-95% of the cluster mass and have NO thermal signature? (Again, IIR, you propose a much smaller percentage of DM - somewhat on the order of 30%, correct?)

I firmly believe that we will find the zero point energy field to be the real player in this regard. Just a tiny difference in infall rates (matter vs anti-matter) could polarize the ZPE EM field in the presence of huge masses, and that polarization should affect the optical properties of space-time. The breaking of this equivalence (matter/antimatter gravitational infall rates) would also provide a mechanism for giving us a matter-dominated universe, in accordance with Smolin's black-hole universe ideas.

The potential energy of the ZPE field is over 120 orders of magnitude too high to account for the cosmological constant, but what if that energy cannot be expressed if the field is randomly oriented? Polarization due to the presence of mass could express some of this energy, even if the infall rates of matter vs antimatter differ by a small amount. Just a thought...

That may be so, but what property of anti-matter would cause it to respond to a gravitational field differently from ordinary matter?

SCC simply takes the Brans Dicke theory, which modifies GR by including a scalar field to fully include Mach's Principle, and modifies it by allowing that field to interact with matter to include the local conservation of energy. We then have a theory that satisfies present experimental tests of the EP, solar system tests of GR and a cosmology that is conformally flat, strictly linearly expansion with a total density, (densities as a proportion of critical density) of 33% of which 11% is ZPE determined by the field equations. Of the remaining 22%, about 20% is baryonic and 1 or 2 % unaccounted for, possibly a neutrino component.
Before WMAP decreed the universe was flat and therefore of 100% density the density of the universe was generally thought to be about a third, luminous density 2%, DM for clusters 20%. ("Inflation is dead, Long live inflation", Scientific American, Science and the Citizen, July 1998 pg. 9) which fits remarkably well with the un-massaged predictions of SCC; that is if the 2% is allow to enlarge to absorb the 20% because of freely coasting nucleo-synthesis.

I do acknowledge the problem of identifying what form the baryonic DM takes, I haven't solved all the problems at once there are some still to chew over!

I am interested in the weak lensing and cluster dynamics results that may be obtained if the assumption is not made that Omega-total = 1, because the WMAP apparent flatness may be explained by conformal geometry.

Garth

 

[Garth]

Garth, I know that you prefer baryonic matter as DM, but what kind of baryonic matter could comprise 90-95% of the cluster mass and have NO thermal signature? (Again, IIR, you propose a much smaller percentage of DM - somewhat on the order of 30%, correct?)

Is it true that the DM has no signature? How dense is the IGM that produces the Lyman alpha forest? Could this be the signature of cold (~3K) gas and metals in the intergalactic voids?

Garth

 

[turbo]

Is it true that the DM has no signature? How dense is the IGM that produces the Lyman alpha forest? Could this be the signature of cold (~3K) gas and metals in the intergalactic voids?

Garth

I'm sure my CiteBase procedure has holes in it (there is TOO MUCH to read!), but so far, I've not seen any signature of CDM cited in the literature, apart from refraction. No cited absorption, diffusion, nor spectral dispersion. CDM can't be matter, unless it the least interactive matter imaginable. ZPE fields, anyone?

 

[Chronos]

Another candidate hot off the presses
http://www.space.com/scienceastronomy/astronomy/dark_matter_001004.html

 

[turbo]

Thank you for the link, Chronos. I'm sure you can think of one source of self-annihilating mass (hint, hint)

Yes, Virginia, there is an aether. Nature abhors a vacuum.

 

[Nereid]

Is it true that the DM has no signature? How dense is the IGM that produces the Lyman alpha forest? Could this be the signature of cold (~3K) gas and metals in the intergalactic voids?

It might be helpful to understand the DM challenge in a little more detail. For example, there is certainly a cosmological aspect - how to account for the angular power spectrum in the CMBR, universal matter density, ... - but there's also a very 'local' DM problem - cluster mass, galaxy mass, ...

As is probably well known (at least to long-time PF readers!), MOND does a good job of accounting for several of the 'local galaxy' DM challenges (by 'local' I mean within a few hundred Mpc, say the nearest dozen or hundred or so superclusters), esp spiral rotation curves. However, it fails completely wrt rich cluster DM. Similarly, there's far too little H in the Lyman alpha forest, locally, for cold atomic H to account for cluster DM (caveat: it's probably still early days - how many detailed UV surveys have been done?). Besides, cluster IGM is very hot - as Chandra and Newton XMM results clearly show. These results also show far too little hot gas for it to be DM. Microlensing surveys (e.g. MACHO, OGLE) rule out compact objects as the DM, at least for the Milky Way halo ... where 'compact objects' is ~0.01 to 10 M_sol (going from memory, it might be an even larger range).

Oh, btw, it's the cluster DM which is the biggest headache for cosmological models, because there's apparently much more of it than galaxy DM, and rich clusters are where most of the action is.

So, what else could the rich cluster DM be? How about a gas or plasma, but not H? IIRC, if H shows up in the Lyman forest, so will just about every other thing ... except He. While some work has been done on He in the IGM, I guess some cluster DM could be cold He (why such gas would be so preferentially enriched with He would be a new mystery, of course).

What else?
- dust grains? No; just as dust is easy to 'see' in a galaxy, it'd be easy to see in a cluster (and we don't see any)
- rocks? Maybe
- 'comets'? Maybe
- 'loose planets'? Maybe
However, all these would introduce pretty big elephants of their own - very peculiar size distributions (e.g. if rocks, why not lots of dust?), the origin of 'metals' in such objects (H and He alone can't form 'rocks' or 'comets'), and so on.

How about turbo-1's favourite - ZPE, or an extension/replacement for GR in rich clusters (and heavy galaxies, and SMBHs)? AFAIK, the problem here is a lack of theory - there's plenty of good, local data that could be used to test any such theories, but where are the theories?

When all else has been eliminated, what remains, no matter how improbable, needs to be taken seriously (who said that?). Axions and wimpzillas anyone?

 

[Garth]

Neried thank you for that analysis.
The standard model has another problem with DM, it predicts that it should be concentrated in glactic centres, 'cusps', which do not appear to be there. See "Cuspy Dark-Matter Halos and the Galaxy" Binney & Evans http://uk.arxiv.org/abs/astro-ph/0108505.

We conclude that the cuspy haloes favoured by the Cold Dark Matter cosmology (and its variants) are inconsistent with the observational data on the Galaxy.

Let me give my ‘hand-waving’ scenario for general discussion and for ‘pulling to pieces’!
.
· The WMAP data is angular in nature, as conformal transformations preserve angles, the observation of flatness is not only consistent with the flat Friedmann model, but also with models that are conformally flat.

· The SCC model is such a conformally flat model; it is a cone in the Einstein frame or a cylinder in the Jordan frame– either can be unrolled along their time-like axis onto a flat sheet.

· However because these models are space-like finite the large angle WMAP anomaly is resolved, because there was not enough room for the very largest fluctuations to form; unlike the infinite flat Friedmann model.

1. The universe consists of, (all densities are percentages of the critical density), 1% neutrino, or thereabouts –estimated from the measured light neutrino mass, 11% ZPE fields & 21% baryonic including high primordial metallicity (note this is gas not dust). No further DM is required.
2. There is no further DE apart from the ZPE fields.
3. The baryonic component is ¾ H and ¼ He as normal.
4. Gravitational collapse, centred on primordial fluctuations, gradually build concentrations of gas. As the temperature and pressure of the primordial gas falls, because of cosmic expansion, so does the Jean’s mass enabling smaller gravitational collapses that will eventually form galactic super-clusters, clusters and galaxies in that order.
5. Much primordial gas remains un-accreted in the IGN.
6. On smaller scales within the cluster Jeans mass massive stars have accreted that go S/N and form black holes, which act as seeds around which galaxies will form.
7. During this period there is re-ionisation of the IGN, after which the IGN continues to cool by cosmic expansion until it reaches a temperature of around 10K (??) in the present epoch.
8. Much of the primordial gas, now ~ 25% seeded by metallicity from Type III stars and galactic out flow from Type II and I stars, remains in the IGN. The signature of this is the Lyman alpha forest.
9. The next densest concentration is in the intergalactic cluster medium, followed by the galactic halo, which comprises of IGN still falling into galactic potential wells.
10. The least dense concentration is in the inner galaxy where it has accreted into stars long ago hence explaining the lack of a DM galactic centre cusp.
11. Local fluctuations of density could cause the primordial gas to form black, holes, Type III stars long expired, Type II stars – also expired(?), brown dwarfs and Jupiters.

The actual history is going to be more complicated than this (and how!) but I offer the above as a rough template. Does it fit?

Garth
P.S. (who said that?) I think it was Sherlock Holmes

P.P.S. Edit - for IGN read IGM (inter galactic medium) - why do I do that?

 

[turbo]

Oh, btw, it's the cluster DM which is the biggest headache for cosmological models, because there's apparently much more of it than galaxy DM, and rich clusters are where most of the action is.

How about turbo-1's favourite - ZPE, or an extension/replacement for GR in rich clusters (and heavy galaxies, and SMBHs)? AFAIK, the problem here is a lack of theory - there's plenty of good, local data that could be used to test any such theories, but where are the theories?

When all else has been eliminated, what remains, no matter how improbable, needs to be taken seriously (who said that?). Axions and wimpzillas anyone?

Thanks for the overview of the problems with DM candidates. None of the candidates that I found proposed in the literature (and there are a LOT of papers that I'm sure I have missed!) were satisfactory, which is why I started following the "ZPE trail" about 6 months ago. Here is where I have gotten so far, and please bear in mind that I'm discussing the EM ZPE field only at this point - particle/antiparticle virtual pairs:

These are only the high points - there are a LOT of strands yet to be included.

1) ZPE is pervasive, but it can be suppressed by confining the space in which the pairs can form (I.E. between the closely-spaced plates in a Casimir force instrument)

2) The ZPE field is repulsive if the particle pairs are randomly oriented or nearly so, as demonstrated by the Casimir effect.

3) The crux of my model is that the gravitational infall rate of antimatter is higher than that of matter. This is where I badly need sufficiently accurate testing - the Cern data are inconclusive. Note that HERE is where the equivalence of inertial mass and gravitational mass is broken. The inertial masses of each member of the virtual particle pair are equivalent, but their gravitational masses are not (due to the extra attraction of antimatter to matter).

4) The infall rate differential causes the ZPE field to assume a preferential alignment in the presence of sufficiently large masses of matter, with the antimatter component of each pair tending to be closer to the dominating mass. Visualize a sea of magnets, then introduce a powerful monopole into the middle of them. They closer magnets would flip into alignment very readily, and the magnets farther and farther out would flip as well, being confronted with a virtual wall of aligned magnets closer back to the monopole. Now instead of magnetism, model this as matter/antimatter attraction (infall).

5) Gravity is caused by the interaction of mass with the ZPE field. The more strongly polarized the ZPE field, the stronger the gravitational effect will be. This explains how clusters can stay together with seemingly insufficient visible matter. It should also be possible to model MOND using polarized ZPE fields in galaxies, but I'm not there yet.

6) Polarization of the ZPE field is equivalent to increasing the density of space-time in that region - light will slow down passing through such a dense field, just like it slows down when encountering the glass lenses of a refractor. Cluster lensing in this model is therefore seen as a function of the density and shape of the lensing region, and not as a purely gravitational effect on light waves.

In summary, exotic DM is not necessary. We already have a suspect capable of causing differential galactic rotation, cluster binding, and cluster lensing. We don't have to invent ZPE - it is demonstrably in existence. We only need to prove that the ZPE fields can be polarized by the presence of mass, and the most intuitive means by which the fields can be polarized is by a differential in antimatter/matter gravitational infall rates. If there is a differential in the infall rates, it's a whole new ball game.

Of course, this model reintroduces the concept of the Aether, and there will be general rending of garments and gnashing of teeth as cosmologists struggle with invariance of the speed of light, no preferred reference frames and the other minor details that ensue.

I am truly sorry that I abandoned math/physics studies in college, for I do not have time to learn the mathematics to do a proper job describing this modeling. Perforce, it's all thought experiments at this stage.

 

[Nereid]

Thanks Garth.

Perhaps I didn't say things very clearly (a situation that is, alas, rather too common); I was taking a bit of an excursion from the cosmological scale, to look at the DM challenges at 'local' scales, and to note these, irrespective of one's favoured cosmological model (of course, that favoured model may include an interpretation of we call 'galaxies' and 'clusters' as something other than gravitationally bound - more or less - bunches of stars, gas, dust, etc; if so, then we would need to have a quite different discussion!).

In your post you use the term 'IGN', but I'm unsure whether you mean the gas between clusters, or within clusters (but not in galaxies), or both - would you mind clarifying please?

To say a few more words about the rich cluster DM:

In another thread we have been discussing the DM profile of a rich cluster, as estimated by the lensing of background objects. In this case, the lensing is a 'mass detector', assuming GR. The mass in a rich cluster can also be estimated by two other, independent methods - application of the virial theorem to observed cluster member velocity dispersions, and hydrodynamic calculations (assume the gas which generates the observed X-rays is in equilibrium). All three methods give roughly the same answers. So, where is the observed (dark) mass? (Segue to my previous post) ... it's not in BH/stars/gas/dust in the galaxies (there's far too little); it's not in the gas between galaxies in the cluster (maybe some caveats?); it's not in dust in between galaxies in the cluster; so where is it?

Just in case the point I'm making isn't clear ... the question of rich cluster DM needs to be addressed no matter what cosmological model you choose to use. Also, at the risk of boring all readers to tears, only baryonic matter in the form of rocks, comets, planets and (maybe) failed stars could escape detection (other than gravitationally), and sufficient quantities of these to make up most of the rich cluster DM would imply all sorts of very odd things.

 

[turbo]

4. Gravitational collapse, centred on primordial fluctuations, gradually build concentrations of gas. As the temperature and pressure of the primordial gas falls, because of cosmic expansion, so does the Jean’s mass enabling smaller gravitational collapses that will eventually form galactic super-clusters, clusters and galaxies in that order.

10. The least dense concentration is in the inner galaxy where it has accreted into stars long ago hence explaining the lack of a DM galactic centre cusp.

Re: number 4 - so much for the heirarchical model under SCC. There appears to be too much structure at early epochs to support the heirarchical model, anyway, so I am uncomfortable with it. My question is does SCC envision an opposite approach, equivalent to fission (condensation, splitting and differentiation) as opposed to the heirarchical "small structures fuse to form larger structures"?

Re: number 10 - I can see how your model can embrace the "hollow" dark matter halos needed to explain the rotations of spiral galaxies. I have difficulty understanding how all that remaining baryonic mass can be around galaxies and in clusters and be indetectable, though. If it is baryonic, It must be warmed enough to re-radiate, or be detectable by spectral absorption or by micro-lensing. This is the primary reason I started tracking ZPE virtual pairs. I was unwilling to accept non-baryonic matter and unable to accept the undetectability of baryonic matter.

 

[meteor]

I for one believe in dark matter. I'm actually reading a bit about profiles for dark matter halos, apart of the NFW profile there's another called Moore profile that can also serve to model CDM halos.Has some member of PF some preference between the NFW profile and the Moore profile?
There's also a profile called King profile that I'm not sure if it's valid to model dark matter halos. Is it?

 

[Garth]

Thank you Nereid.
[Sorry - I've added an edit to my previous post - IGN should be IGM! and refers primarily to the inter-cluster medium in deep space.]

However from this source IMHO Jean's masses would have collapsed down to cluster, and then galactic masses.

I agree that in whatever model there is a problem. However with the Lyman alpha forest, which is a signature of cold hydrogen gas in the deep space inter-cluster voids, and the rich cluster x-ray emission, which is the signature of hot ionised plasma within the cluster, there is some evidence of the matter in these mediums.

I find it hard to believe that much of it would have collapsed into Jupiters or failed stars so yes I do agree there is a considerable problem. I suppose I am appealing to Ockham's (Occam's) razor to go for the option that requires less unknown "entities".
- Garth

 

[Chronos]

The king profile assumes an inner slope dark matter density profile of 0, as compared to 1.0 for NFW and 1.5 for Moore. The calculation is otherwise the same. The higher the slope, the more peaked the matter distribution towards the center. The 'best fit' profile appears to vary depending on age and level of interaction between structures. Older, less interactive structures tend to be flatter [king profile] whereas younger, more interactive structures tend toward steeper distributions.

 

[meteor]

Good Job Chronos!
There's also another profile used to describe dark matter halos: the Hernquist profile (Hernquist, 1990)

 

[Mike2]

The king profile assumes an inner slope dark matter density profile of 0, as compared to 1.0 for NFW and 1.5 for Moore. The calculation is otherwise the same. The higher the slope, the more peaked the matter distribution towards the center.

I must have missed something. Do you have a link to these different DM models? Could you explain a little more about this "slope"? Thanks.

The 'best fit' profile appears to vary depending on age and level of interaction between structures. Older, less interactive structures tend to be flatter [king profile] whereas younger, more interactive structures tend toward steeper distributions.

As far as the lensing effect goes, could it be possible that the older clusters are traveling faster (more redshifted) and so light has more time to feel the gravity of these older galaxies as they pass by? Whereas the younger galaxies are moving much slower compared to these early ones so that light feel these younger galaxies as if those galaxies were more or less standing still?

Did I read right that it is only the spiral galaxies that show more lensing effect than expected?

 

[Chronos]

I must have missed something. Do you have a link to these different DM models? Could you explain a little more about this "slope"? Thanks.


As far as the lensing effect goes, could it be possible that the older clusters are traveling faster (more redshifted) and so light has more time to feel the gravity of these older galaxies as they pass by? Whereas the younger galaxies are moving much slower compared to these early ones so that light feel these younger galaxies as if those galaxies were more or less standing still?

Did I read right that it is only the spiral galaxies that show more lensing effect than expected?

Start here
http://www.mrao.cam.ac.uk/~hjb26/thesis/node6.html

 

[Nereid]

Did I read right that it is only the spiral galaxies that show more lensing effect than expected?

yanniru stated this, but when I checked the paper from which he got the idea, I found it referenced only one source, and upon checking that I found the study was limited to three, carefully selected ellipticals, none of which seemed to have a DM profile of the kind predicted. However, the authors of this study did clearly state that other work had found strong evidence of DM profiles (as predicted by LCDM models?) in both massive (cD) and dwarf ellipticals. If you look at the cluster analysis done by the Bell Labs team, you will see that plenty of the ellipticals generate lensing signals. IIRC, an early SDSS statistical study also found that lensing was pretty much independent of Hubble type (it would be interesting to see this work repeated with the newer SDSS releases, and the aggregated data). Of course, this work was statistical, so there is probably no easy way to extract galaxies which show much less lensing than expected (or maybe not ... anyone interested to work out an algorithm? anyone have access to the necessary resources to do the work?? Join PF and do some real, on-line science?)

 

[turbo]

How about turbo-1's favourite - ZPE, or an extension/replacement for GR in rich clusters (and heavy galaxies, and SMBHs)? AFAIK, the problem here is a lack of theory - there's plenty of good, local data that could be used to test any such theories, but where are the theories?

I don't know what these authors are using for a justification for their proposed antimatter gravity experiment, although I hope they get the funding they need to pull it off. I have been trying to find a non pay-per-view version of this article on-line. Kluwer won't let me read the article unless I pay them $25. Can someone with a subscription summarize the authors' proposal and their justifications for me? Specifically, I would like to know why they want to measure the fall rate of antimatter.

BTW, Ingenta has the article, too, but they won't let me read it unless I pay them $31. They have a lot of articles regarding experimentation on the ISS, but at $31 each, I can't afford to read them.

http://ipsapp009.kluweronline.com/IPS/content/ext/x/J/4728/I/87/A/6/abstract.htm

http://www.ingenta.com/isis/browsing/TOC/ingenta?issue=pubinfobike://klu/gerg/2004/00000036/00000003

 

[Mike2]

yanniru stated this, but when I checked the paper from which he got the idea, I found it referenced only one source, and upon checking that I found the study was limited to three, carefully selected ellipticals, none of which seemed to have a DM profile of the kind predicted. However, the authors of this study did clearly state that other work had found strong evidence of DM profiles (as predicted by LCDM models?) in both massive (cD) and dwarf ellipticals. If you look at the cluster analysis done by the Bell Labs team, you will see that plenty of the ellipticals generate lensing signals. IIRC, an early SDSS statistical study also found that lensing was pretty much independent of Hubble type (it would be interesting to see this work repeated with the newer SDSS releases, and the aggregated data). Of course, this work was statistical, so there is probably no easy way to extract galaxies which show much less lensing than expected (or maybe not ... anyone interested to work out an algorithm? anyone have access to the necessary resources to do the work?? Join PF and do some real, on-line science?)

I wonder how fast the earliest galaxies were moving. It is supposed that the universe was decelerating in expansion from the beginning (until recently it has started to accelerate). So presumably galaxies were moving at their fastest speed when they first formed. Since it takes time for background light to pass a foreground galaxy, and foreground galaxies are traveling in the same direction as background photons (outward direction), would those background photons feel the gravity of those foreground galaxies for a longer period of time and be bent around those galaxies more than if the foreground galaxy was standing still? How fast were these foreground galaxies moving at the time the background photons were passing by? Do the computer simulation assume any significant speed of the foreground galaxies? Is the over lensing effect less profound for nearby galaxies? Thanks.

 

[Chronos]

Given the speed of light is invariant, the relative motion of galaxies in the foreground is of no consequence. Only mass need be considered for lensing effects.

 

[turbo]

Given the speed of light is invariant, the relative motion of galaxies in the foreground is of no consequence. Only mass need be considered for lensing effects.

There are some pretty smart people who disagree with you. They think the speed of light might be determined by the texture of the space-time that the light has to cross.

http://arxiv.org/abs/hep-th/9408016

http://arxiv.org/abs/gr-qc/9504041

http://arxiv.org/abs/astro-ph/0001441

The fact that "empty" space is actually a sea of virtual particles is proof that there is an aether. Densification or polarization of this field has implications for the refractive properties of space-time. Lenses are arrangements of matter in which the speed of light is slower (in our real world) than that of the SOL in a "vacuum". By extension, the space-time properties in very massive clusters (caused by ZPE gradients) should produce refractive effects that cannot be explained by the visible matter in the cluster.

 

[Mike2]

Given the speed of light is invariant, the relative motion of galaxies in the foreground is of no consequence. Only mass need be considered for lensing effects.

Granted that if the first early galaxies were moving very slowly with respect to light, then lensing would not be affected by the motion of the foreground galaxy. But I do not know how fast early galaxies were moving, do you? But if there were moving at some portion of light, say 1/3 that of light, then the backgound photons would feel the force of gravity for a longer period of time and be deflected more. I don't see yet what invariance would have to do with anything. Not only that, but the galaxies would acquire some portion of relativistic mass and the gravitational field associated with that.

 

[selfAdjoint]

Granted that if the first early galaxies were moving very slowly with respect to light, then lensing would not be affected by the motion of the foreground galaxy. But I do not know how fast early galaxies were moving, do you? But if there were moving at some portion of light, say 1/3 that of light, then the backgound photons would feel the force of gravity for a longer period of time and be deflected more. I don't see yet what invariance would have to do with anything. Not only that, but the galaxies would acquire some portion of relativistic mass and the gravitational field associated with that.

Surely the galaxies' own local motions were far less than c, and if you mean motion due to expansion, of course the galaxies were not and are not moving in that sense. Space is expanding, the remote galaxies are no more moving like that than we are.

 

[Chronos]

Granted that if the first early galaxies were moving very slowly with respect to light, then lensing would not be affected by the motion of the foreground galaxy. But I do not know how fast early galaxies were moving, do you? But if there were moving at some portion of light, say 1/3 that of light, then the backgound photons would feel the force of gravity for a longer period of time and be deflected more. I don't see yet what invariance would have to do with anything. Not only that, but the galaxies would acquire some portion of relativistic mass and the gravitational field associated with that.

Galaxies moving slowly with respect to light? Light does not have a preferred reference frame. That is why the speed of light is called 'invariant'. And yes, I do know, given what I have read, how fast galaxies were moving in the past. It is called red shift. Your photon deflection model is not supported. Photons entering a gravitational field are blue shifted. When they exit, they are red shifted. The net effect is... zero.

 

[Chronos]

The fact that "empty" space is actually a sea of virtual particles is proof that there is an aether.

Really? That is a pretty bold assertion. Which version of aether do you have in mind, Lorentzian?

 

[turbo]

Really? That is a pretty bold assertion. Which version of aether do you have in mind, Lorentzian?

It's not bold at all. The vacuum of space is not empty, but is populated by zero-point energy fields. The EM ZPE field consists of a sea of self-annihilating virtual particle pairs, and this field exerts a measurable force, as demonstrated by the Casimir effect.

If you know anything about optics, you will know that light travels at different speeds in media of different densities. If you will glance at the papers I linked above, you will see that I am not the only person who has made the logical extension and arrived at the understanding that the speed of light can be affected by the density of the ZPE field through which it propagates. In fact, light propagating through a suppressed ZPE field (between the plates of a Casimir device) can be shown to travel faster than the speed of light in a "vacuum" (normal ZPE field).

"Empty" space isn't. The ZPE field predicted by QED has been proven to exist and its pressure has been measured using test equipment of various designs - not just the "two flat plates" configuration of the first model.

 

[Mike2]

Surely the galaxies' own local motions were far less than c, and if you mean motion due to expansion, of course the galaxies were not and are not moving in that sense. Space is expanding, the remote galaxies are no more moving like that than we are.

Well, let's see... durring inflation all matter was moving very fast, right? Then the force of gravity slowed matter even while it condensed to galaxies. I still don't know how fast those first galaxies were moving? Or was everything moving very slowly in comoving coordinates even during inflation?

 

[wolram]

If DM is cold and dark, how can it be proven, detected, if something most
think of as invariable isn't "c" for instance, please forgive my ignorance, but
it seems to me that this is a circular argument.

 

[Chronos]

Well, let's see... durring inflation all matter was moving very fast, right? Then the force of gravity slowed matter even while it condensed to galaxies. I still don't know how fast those first galaxies were moving? Or was everything moving very slowly in comoving coordinates even during inflation?

Agreed. They were moving very slowly in comoving coordinates even during inflation. As selfAdjoint pointed out, there is no evidence to suggest relativistic contributions to the mass of distant galaxies are any greater than for local galaxies [which is insignificant]. Cosmological red shift does not affect relativistic mass. Returning to the question of lensing of the CMBR, which is also relevant, see here.
http://home.fnal.gov/~scranton/LensedCMB/effect.html

If DM is cold and dark, how can it be proven, detected, if something most think of as invariable isn't "c" for instance, please forgive my ignorance, but
it seems to me that this is a circular argument.

Agreed. If 'c' is not invariant, a lot of modern theory turns into a mess. On the other hand, there is good evidence that 'c' has not detectably changed for billions of years, if ever [there are some possible anomalies if you go back 12 billion or so years].

 

[turbo]

Agreed. If 'c' is not invariant, a lot of modern theory turns into a mess. On the other hand, there is good evidence that 'c' has not detectably changed for billions of years, if ever [there are some possible anomalies if you go back 12 billion or so years].

C may be invariant over time. Time (history) may be irrelevant. C must be variable, however, based on the density of the media through which light propogates (basic optics). If the vacuum of space is not truly a "void", but in fact contains fields defined by the base-level energies predicted by QED (the zero-point energy fields), we must expect that the light propogating through these fields can be effected by the properties of these fields.

C as defined as "the speed of light through a vacuum" may only be an ideal, never to be reached. The real C (as a cosmological speed limit) may only be a virtual entity, with a serious dependence on conditions.

 

[Mike2]

Returning to the question of lensing of the CMBR, which is also relevant, see here.
http://home.fnal.gov/~scranton/LensedCMB/effect.html

This seems to suggest that the CMB is a backdrop farther away than the most distant galaxies? I didn't catch how much farther they assume the CMB to be. Nor did they explain how all this light got that far out? But, then again, they admit that this is only a simulation and that we do not yet possesses the capability to measure the CMB accurately enough to confirm this lensing of the CMB.

But wait, if the CMB photons were traveling since the beginning without scattering, then the photon that WE receive from the CMB must be the oldest photons of all. The photons from the photon soup that originate at every point and has been redshifted by expansion have photons originating at all points of space, but we only see those that are as old as recombination. CMB photons that were emitted nearer to us at the time of recombination have already past us by and are now headed away from us. We only see the oldest of the CMB. So we are seeing a backdrop. Is this right? Why does it seem that I have to be the one to explain everything?

What confuses me is if we can see these photons emitted so far away by the CMB, then how can there be any kind of horizon that is closer to us behind which galaxies are disappearing? Or is it that the CMB that we see IS the horizon. If so, then shouldn't it be even colder, in fact zero? Or will there come a time when we will no longer see the CMB? Or will the faint, red light of other galaxies take its place as the universe expands?

 

[Chronos]

This seems to suggest that the CMB is a backdrop farther away than the most distant galaxies? I didn't catch how much farther they assume the CMB to be. Nor did they explain how all this light got that far out? But, then again, they admit that this is only a simulation and that we do not yet possesses the capability to measure the CMB accurately enough to confirm this lensing of the CMB.

Agreed. The CMB is a backdrop to the most distant galaxies yet observed. The current suspect for most distant observed galaxy is z = 10. The CMB is around z = 1100.

But wait, if the CMB photons were traveling since the beginning without scattering, then the photon that WE receive from the CMB must be the oldest photons of all. The photons from the photon soup that originate at every point and has been redshifted by expansion have photons originating at all points of space, but we only see those that are as old as recombination. CMB photons that were emitted nearer to us at the time of recombination have already past us by and are now headed away from us. We only see the oldest of the CMB. So we are seeing a backdrop. Is this right?

Agreed.

Why does it seem that I have to be the one to explain everything?

That is just the way it works. You shouldn't believe anything until you can explain it to yourself.

What confuses me is if we can see these photons emitted so far away by the CMB, then how can there be any kind of horizon that is closer to us behind which galaxies are disappearing?

Agreed. It's not possible.

Or is it that the CMB that we see IS the horizon.

Yes.

If so, then shouldn't it be even colder, in fact zero?

No. It is exactly as cold as it should be given the age of the universe. The CMB photons we now detect had a temperature of about 3000k at the time they were emitted. The only thing that cools them down is red shift. Since they now are about a temperature of 2.75K, we know that recombination occurred at around z = 1100 [which blue shifts them back to the time they had a temperature of about 3000k].

Or will there come a time when we will no longer see the CMB? Or will the faint, red light of other galaxies take its place as the universe expands?

The CMB will gradually grow cooler and cooler, always approaching but never quite reaching absolute zero. No new galaxies will emerge from behind the CMB barrier.

 

[Mike2]

Chronos, you seem to be saying on the one hand that there is no horizons beyond which galaxies disappear. But on the other hand, you're saying that there is an expansion of the universe that can be faster than light. Or are you denying that the universe can expand faster than light? Where would that leave inflation? But if the universe can expand faster than light, then the photons from those regions will never reach us, right?

 

[Garth]

We have had this discussion before in the thread “Time Dilation & big bang Question”

First the CMB is not an event or particle horizon, in that radiation from beyond the surface of last scattering (SLS) still reaches us, it is just continuously scattered until it finally reaches the SLS. That is why the temperature of the CMB is not zero.

Whether objects in front of that scattering, whose red shifts are finite, are actually traveling faster than light or not depends on how you measure their velocity. That is, how you define and measure distance and time across the space-time curvature and cosmic expansion. One standard convention is to say you can observe cosmologically super-luminal objects. See http://bat.phys.unsw.edu.au/~charley/papers/0310808.pdf
Garth