Is the Universe Really Expanding?

[Garth]

Chronos "Can we talk about spallation yet?"
Deuterium is very fragile.
The standard model assumes that any deuterium left today has been left over from the BB as any other source, such as stellar nuclear fusion reactor cores, would not only have created deuterium but destroyed it ‘instantly’ as well.

The deuterium relative abundance (D/H ~ 2 x 10 ^-5) is therefore assumed to be a very accurate trace of what was happening in the BB and puts a fine constraint on cosmological constraints. (1% < Omega_baryonh² < 1.5%) (h² ~ 0.5) It is more or less concordant with a 3% - 4% baryon closure density.

If another significant source of deuterium exists then that would throw this standard model out.

Deuterium production by high-energy particles

The production of the cosmic abundance of deuterium by high-energy spallation reactions is examined. The large energy requirements and the concomitant production of other nuclei and gamma-rays impose severe constraints on this sort of mechanism. Violent pregalactic events, which might occur shortly after recombination or in early quasarlike objects, are found to be possible sites for deuterium production. Some constraints on the origin of the diffuse gamma-ray background also are obtained.

The question is; how significant are these other possible sites for deuterium production? If the D/H ratio is partly explained by such then the standard model has some explaining to do. If all the D/H ~ 2 x 10 ^-5 can be explained in this way then nucleosynthesis might continue in a more slowly evolving universe and produce all the DM as baryons, but that would not be "mainstream cosmology".

Garth

 

[meteor]

Another question [pardon my curiousity], could SMBH have formed in the early universe from collapsing gas clouds [skipping the merger thing, just formed directly]?

I find myself quite skeptical with respect to the possible formation of black holes if that formation doesn't come from one of these two processes:
a)the collapse of a star
b)the formation of miniblackholes in the early stages of the Universe

though I have read some other persons proposing that it could be possible the formation of a black hole by the collapse of a cloud, these propositions have been in Internet forums, so possibly only based in wild speculation, but then I've found this paper in arxiv
http://arxiv.org/abs/astro-ph/0505136
Black Hole Formation from Collapsing Dark Matter in the Background of Dark Energy

that more or less proposes that black holes can be formed if a cloud of dark matter and dark energy collapses. Given that dark matter halos were one of the first structures to form in the Universe, then this paper open the door to the possibility that some massive black holes in the center of galaxies could have formed this way. I'm by no means subscribing to the point of view of the authors of the paper, only presenting a curious theory

 

[Garth]

There is another problem with SMBH's - the formation of the BH, either from the end result of super massive stars, or directly from DM & DE, which would also drag a lot of baryonic matter with it, would be a very energetic and bright event. Should we be seeing these very early hyper-novas?

That something did go on in the pre-galactic era seems very likely as there is a lot of re-ionisation and early metallicity to explain. However if there were a few very large BH formation events then the re-ionisation and metallicity would be very localised and patchy. This does not seem to be the case, although there is variation in the metallicity.

Perhaps these events were not as large as the SMBH scenario requires, and there were many more of them. IMBHs ([10² - 10⁴]M_solar) could explain the DM today.

Garth

 

[Chronos]

One of the problems with finding very low or metal free galaxies is low metallicity results in low surface brightness. Low metallicity galaxies are progressively under represented in surveys as redshift increases. They could be very numerous at z=6+, but are simply too faint to be seen.

 

[Garth]

So the "Mainstream Cosmology" model predicts:
1 Large SMBH's, but their bright formation process has not been observed - too faint?
2 An evolution in early metallicity - but that has not been observed - selection effect?
3 The vast proportion of the universe 73% in the form of Dark Energy - but nobody has any idea of what that actually is and certainly have not verified its existence in a laboratory or Earth bound observation.
4 23% of the universe in the form of non-baryonic Dark Matter - but nobody has any idea of what form that might take - ditto as with DE.
5 A process of explosive Inflation in the earliest universe because of the action of the Higgs field - but nobody has discovered the Higgs boson that causes that process.
6. A antigravity effect that causes acceleration of the expansion of the universe - DE? - this effect is massively switched on in the Inflation epoch, switched off for the nucleosynthesis epoch, switched on for the distant SN Ia epoch and finally switched off again for the recent epoch.

All to make the mainstream cosmological model fit the data.

Am I being too critical in my analysis of that model? Perhaps I am a natural cynic, but then again perhaps not.
Just a few thoughts.

Garth

 

[Chronos]

Just focusing on metallicity issues for now, Garth. It has been notoriously difficult to obtain good metallicity samples. Reliable, low z sources are rare and high z sources are contaminated by selection effects [low metallicity galaxies are inherently fainter]. The data is, however, accumulating and evolutionary trends are emerging:

The Age-Metallicity Relation of the Universe in Neutral Gas: The First 100 Damped Lya Systems
http://arxiv.org/abs/astro-ph/0305314

Chemical Abundances in SFG and DLA
http://arxiv.org/abs/astro-ph/0504389

Damped Lyman Alpha Surveys and Statistics - A Review
http://arxiv.org/abs/astro-ph/0505479

 

[Garth]

Chronos yes, I am not arguing that there has been no metallicity evolution as I believe red shift to be cosmological, and therefore high z systems are ancient. Since then stellar nucleosynthesis has obviously taken place after all the stars are luminous! I was exaggerating for the sake of making a point in my (2) above.

The question is; "At what high z does the standard model expect this metallicity to drop to zero and is this bottoming out observed?" Your first link above states

Regarding the lower limit to the DLA metallicities, it appears possible that we will never identify a damped LyA system with [M/H] < −3, a value that significantly exceeds our detection limit. This lower bound has important implications for the presence of primordial gas (zero metallicity) within these galaxies. If primordial gas with significant surface density and cross-section exists in high redshift galaxies, then it is always surrounded by metal-enriched gas yielding a mass weighted metallicity exceeding 1/1000 solar.

Note the assumption that primordial gas has to have zero metallicity. It is precisely this assumption that is cosmological model dependent and that which I question.

Garth

 

[SpaceTiger]

All to make the mainstream cosmological model fit the data.

These things were invented to explain the data, not the other way around.

1 Large SMBH's, but their bright formation process has not been observed - too faint?
2 An evolution in early metallicity - but that has not been observed - selection effect?

Again, I think it's really silly that crackpots put so much emphasis on these observations as evidence for non-standard cosmology. They're extremely sketchy and littered with selection biases. The mainstream model does not claim to have a solid understanding of the process of quasar growth or metallicity evolution, so it should be of no surprise that they produce difficult observations.

3 The vast proportion of the universe 73% in the form of Dark Energy - but nobody has any idea of what that actually is and certainly have not verified its existence in a laboratory or Earth bound observation.

"Dark energy" is little more than a description of an observation at this point. We don't have a solid theory for it yet, so emphasizing its non-detection is redundant.

4 23% of the universe in the form of non-baryonic Dark Matter - but nobody has any idea of what form that might take

That's untrue. In fact, particle physicists expect a particle at exactly the energy scale needed to solve the dark matter problem. Furthermore, alternative gravity models have not successfully predicted (or even explained) all of the observed phenomena. More on this later.

5 A process of explosive Inflation in the earliest universe because of the action of the Higgs field - but nobody has discovered the Higgs boson that causes that process.

The evidence for an inflationary epoch is getting stronger, but is still not entirely convincing. Again, more on this later.

6. A antigravity effect that causes acceleration of the expansion of the universe - DE? - this effect is massively switched on in the Inflation epoch, switched off for the nucleosynthesis epoch, switched on for the distant SN Ia epoch and finally switched off again for the recent epoch.

The standard model has the current acceleration being caused by dark energy and the inflationary epoch by some other scalar field. This point is redundant with those two previous ones.


Many of the things people refer to as "holes" in the standard model are not actually inconsistencies, just things that are not completely understood (like dark energy). The simple fact is that the standard model uses known physics (i.e. GR and QFT) to explain multiple independent observations. This is what makes it so compelling. That we don't have a full understanding of everything should hardly be surprising. Most alternative models invoke arbitrary new physics, usually with serious observational inconsistencies. I doubt that we have everything figured out; in fact, I hope that we don't. I do think, however, that we have done a fairly good job of parameterizing the universe so far and it's clear that the community has been approaching consensus on the basic cosmological parameters. Currently, the only inconsistencies in the standard model are either barely significant or explainable by alterations in less fundamental theories (such as quasar growth).

 

[SpaceTiger]

6) The Matter Density

The matter density is, quite simply, the average space density of matter in the universe. It is usually parameterized relative to the critical density:

\Omega_m=\frac{\rho_m}{\rho_c}

This is the density of all non-relativistic matter, including the stuff we're made of (baryonic matter) and the dark matter that has so far eluded our detectors. It does not include photons, relativistic particles, or dark energy.

Since it includes the stuff we can't see, the estimates of \Omega_m must be dynamical; that is, they must be inferred from gravitational influence of the matter. Doing this in a variety of systems (on both small and large scales), we can directly measure the total amount of matter in the universe. These methods tend to give values in the range:

\Omega_m \sim 0.2 - 0.3

Remember that \Omega_m=1 would mean that the matter density was exactly sufficient to flatten the universe. Recently, several other independent measurements, including the peculiar velocity field of galaxies, the power spectrum, and the CMB, have given values that are in the same ballpark. In fact, measurements of the matter density have been confirmed in so many different ways that it was previously believed that we lived in an open universe with \Omega\simeq \Omega_m \simeq 0.3. With the recent CMB and supernovae measurements, however, we now believe that the remainder of the energy density required to flatten the universe is in some other form, this mysterious dark energy.

 

[SpaceTiger]

There is another problem with SMBH's - the formation of the BH, either from the end result of super massive stars, or directly from DM & DE, which would also drag a lot of baryonic matter with it, would be a very energetic and bright event.

The whole point of dark matter is that it's weakly-interacting and therefore does not emit much light. The collapse of an overdensity consisting only of dark matter would not need to emit a lot of observable photons. Likewise, there's no reason that a dark energy field should have to produce photons upon collapsing to a black hole.

Should we be seeing these very early hyper-novas?

It's hard enough to detect supernovae out to z=1, I don't know why you'd expect to see them at z>6.

That something did go on in the pre-galactic era seems very likely as there is a lot of re-ionisation and early metallicity to explain. However if there were a few very large BH formation events then the re-ionisation and metallicity would be very localised and patchy. This does not seem to be the case, although there is variation in the metallicity.

I can't emphasize enough how sketchy our observations of that era are. To be honest, I don't even entirely trust the WMAP reionization results.

Perhaps these events were not as large as the SMBH scenario requires, and there were many more of them. IMBHs ([10² - 10⁴]M_solar) could explain the DM today.

How many times do I have to emphasize that this thread is not the place for your pet theories? Stop trying to plug your model in my thread.

 

[Garth]

In my posts #35 & #37 I raise questions about the "mainstram cosmology" model. Questions that are raised by others in the cosmological community. These questions might well be answered in the future within that paradigm.

But at what point did I plug my model?

Surely the test of a robust model is that it is open to cross examination?

These things were invented to explain the data, not the other way around.

Stand back and think!

Garth

 

[SpaceTiger]

In my posts #35 & #37 I raise questions about the "mainstram cosmology" model. Questions that are raised by others in the cosmological community. These questions might well be answered in the future within that paradigm.

What's your point?

But at what point did I plug my model?

I quoted it. The IMBH as DM is purely speculation that you've recently introduced as part of your attempt to do away with non-baryonic matter.

Stand back and think!

It's amusing to me how crackpots try to defend their point of view by playing "open-minded", yet seldom seem to understand the observational evidence for the models they're trying to topple. I suppose it hasn't occurred to you that I actually have thought about my opinions? Do I strike you as the sort who's ignorant of the observational support for our current theoretical understanding? Have you heard me give resounding support for every mainstream model? (hint: do a search for my posts on inflation)

 

[Garth]

SpaceTiger I appreciate all that you have said on these Forums and the considerable thought that you have demonstrated in your clear and informative posts.

Nevertheless, in astrophysics and cosmology we are dealing with data that has to be interpreted as "Remote Sensing". The problem with such remote sensing is that of "Ground Truth"; in our case the task of explaining the physics of the cosmos ‘out there’ by the physics of the laboratory ‘down here’.

Today there is a huge amount of precision data, which has to be interpreted, but the interpretation of that data set is theory dependent. i.e. Change the paradigm and that interpretation changes too.

Therefore a critical analysis of the subject has to be open to other possible interpretations, if only to subsequently reject them as internally inconsistent, non-concordant with the data set, incompatible with laboratory experiment and finally inelegant i.e. requiring a multiplication of “entities” [Ockham’s (Occam’s) razor ”Entia non sunt multiplicanda praeter necessitatem” (Entities should not be unnecessarily multiplied).

Let me repeat for clarification – I was not trying to be rude -

These things were invented to explain the data, not the other way around.

As in ‘epicycles’?

Garth

 

[SpaceTiger]

Today there is a huge amount of precision data, which has to be interpreted, but the interpretation of that data set is theory dependent. i.e. Change the paradigm and that interpretation changes too.

If you wish to entirely change a paradigm, you must re-interpret all of the observational evidence in the context of the new paradigm before you can safely say that your theory is viable. This is what Einstein did with relativity; in fact, he went a step further and made predictions. None of the alternative theories on the table have done this successfully, even MOND. I will consider any alternative theory that is prepared to do this, provided that it doesn't arbitrarily "invent" too many new forces, effects, etc.

Therefore a critical analysis of the subject has to be open to other possible interpretations, if only to subsequently reject them as internally inconsistent, non-concordant with the data set, incompatible with laboratory experiment and finally inelegant i.e. requiring a multiplication of “entities” [Ockham’s (Occam’s) razor ”Entia non sunt multiplicanda praeter necessitatem” (Entities should not be unnecessarily multiplied).

I am open to new interpretations, but that's not the point of this thread, as I very clearly stated at the beginning. The point of this thread is to review why we believe or disbelieve the standard model, not to present alternatives to it.

Let me repeat for clarification – I was not trying to be rude -
As in ‘epicycles’?

They are indeed analogous to epicycles, but really, the vast majority of new phenomena are explainable by small extensions to existing theories. There have as yet been no Keplers to come forward and reinterpret everything within a simpler and predictive framework. In the absence of a viable alternative theory, adding components to the existing ones (which have already been tested) is not necessarily an unwise thing to do. If I discover a new star that isn't described by existing theory, should my first instinct be to rewrite stellar astrophysics? That's really not good critical thinking, IMO.

It's one thing to remain skeptical, it's another to have an axe to grind. Despite the "epicycles", the standard model has, so far, been consistent. Unlike Ptolemy, we've only had to add two or three. If that turns out to be sufficient (or, even better, we detect dark matter and/or dark energy), I will not see a need to revise our physics. Till then, if you have new models, I suggest you make predictions (in a separate thread, please) and wait for them to be tested.

 

[turbo]

The whole point of dark matter is that it's weakly-interacting and therefore does not emit much light. The collapse of an overdensity consisting only of dark matter would not need to emit a lot of observable photons.

If dark matter is so weakly interacting as to be undetectable to us, how can it be persuaded to distribute itself "just so" to flatten the rotation curves of galaxies, provide gravitational binding forces for clusters, etc?

 

[Garth]

SpaceTiger my question here is not the acceptance of the standard model, but the confidence placed in that acceptance. While the Higgs boson, the DM particle and the nature of DE are all undiscovered, the veracity of the concepts of inflation, DM and DE must be open to question.

In this thread are we not even allowed to question that "mainstream model"? You seemed to take exception to my doing just that in my posts above.
To be specific:

Perhaps these events were not as large as the SMBH scenario requires, and there were many more of them. IMBHs ([10² - 10⁴]M_solar) could explain the DM today.

How many times do I have to emphasize that this thread is not the place for your pet theories? Stop trying to plug your model in my thread.

Actually I was reflecting on your post #30 in the 'Dark Matter!' thread.

For discussion of observational constraints on black holes as dark matter, see here . Basically, the only workable regime is ~100 - 10⁴ solar masses.

Which I found to be an extremely interesting piece of information that might explain the problem of IGM metallicity and re-ionisation.

Garth

 

[SpaceTiger]

If dark matter is so weakly interacting as to be undetectable to us, how can it be persuaded to distribute itself "just so" to flatten the rotation curves of galaxies, provide gravitational binding forces for clusters, etc?

They're not weakly interacting gravitationally. In that respect, they act the same as any other form of mass/energy. A spherical "halo" is a natural configuration for a collection of bodies interacting only by the gravitational force.

 

[SpaceTiger]

SpaceTiger my question here is not the acceptance of the standard model, but the confidence placed in that acceptance. While the Higgs boson, the DM particle and the nature of DE are all undiscovered, the veracity of the concepts of inflation, DM and DE must be open to question.

In this thread are we not even allowed to question that "mainstream model"? You seemed to take exception to my doing just that in my posts above.

I only take exception to your use of my thread to push obscure and untested ideas (like IMBHs as dark matter).

Actually I was reflecting on your post #30 in the 'Dark Matter!' thread.
Which I found to be an extremely interesting piece of information that might explain the problem of IGM metallicity and re-ionisation.

Not within the standard model. This idea only makes any sense in the context of your cosmology and that's why I take exception to you bringing it up. If you want to discuss it, do so somewhere else.

 

[Garth]

The whole point of dark matter is that it's weakly-interacting and therefore does not emit much light. The collapse of an overdensity consisting only of dark matter would not need to emit a lot of observable photons. Likewise, there's no reason that a dark energy field should have to produce photons upon collapsing to a black hole.

However, as you have said

They're not weakly interacting gravitationally

So as the DM/DE collapsed it would attract also whatever baryonic matter was around. This matter would also be collapsed into a very small volume under extremely high temperatures and pressures and presumably form some kind of supernova. It would very likely be a bright event, would it not?

Garth

 

[Garth]

Actually I was reflecting on your post #30 in the 'Dark Matter!' thread.
Which I found to be an extremely interesting piece of information that might explain the problem of IGM metallicity and re-ionisation.

Not within the standard model. This idea only makes any sense in the context of your cosmology and that's why I take exception to you bringing it up. If you want to discuss it, do so somewhere else.

Alright, how does the standard model explain early metallicity and re-ionisation?

Garth

 

[SpaceTiger]

Alright, how does the standard model explain early metallicity and re-ionisation?

Simple, population III stars. WMAP measures reionization to occur at z~20, indicating that there were a considerable number of stars around before the high-z quasars were observed (z~6). A stellar population can build up supersolar metallicities in 300 Myr with sufficient quantities of star formation. See here:

http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002AJ...123.2151P&amp;db_key=AST&amp;high=42a9f128e013453

Do I think we understand these things? Heck no, but I certainly don't think there is strong evidence for a theoretical contradiction, particularly on the cosmological front.

 

[SpaceTiger]

However, as you have said So as the DM/DE collapsed it would attract also whatever baryonic matter was around. This matter would also be collapsed into a very small volume under extremely high temperatures and pressures and presumably form some kind of supernova. It would very likely be a bright event, would it not?

Did you actually read the paper (or my post, for that matter)? They were talking about the direct collapse of dark matter and dark energy only. If baryons are included, then the process is the usual star formation process.

 

[Garth]

Yes indeed I did read that paper, but how would stop ordinary matter also being dragged in?

Garth

 

[SpaceTiger]

Yes indeed I did read that paper, but how would stop ordinary matter also being dragged in?

That's what makes the paper so implausible. It's hard to imagine a situation in which dark matter and energy will exist in isolation of baryonic matter. I think it was only being presented as a theoretical exercise, determining what would happen if there were only dark matter and/or dark energy. I think it's fair to say that the only plausible methods of BH formation at this point are stellar collapse or relics from the early universe.

 

[Garth]

So a more realistic exercise would conclude that such DM/E BH formation would be bright?

Garth

 

[SpaceTiger]

So a more realistic exercise would conclude that such DM/E BH formation would be bright?

No, a more realistic exercise would be star formation, as I said. The self-interaction of associated baryons prevents large concentrations of DM or DE from collapsing directly into black holes. Instead, black holes must form by the process of star formation.

 

[Garth]

From ST's link in post #51

The results are indistinguishable from those of lower redshift quasars and indicate little or no evolution in the metal abundances from z~6 to 2. The line ratios suggest supersolar metallicities, implying that the first stars around the quasars must have formed at least a few hundreds of mega years prior to the observation, i.e., at redshifts higher than 8.

Interesting! - Over to Chronos?.

Garth

 

[Garth]

ST what mass range of PopIII stars are we talking about and what would they bequeath to the present epoch?

Garth

 

[turbo]

They're not weakly interacting gravitationally. In that respect, they act the same as any other form of mass/energy. A spherical "halo" is a natural configuration for a collection of bodies interacting only by the gravitational force.

Are you saying that the dark matter halos are naturally spherical, and that the spherical distribution can account for the galactic rotation curves of all galaxies? My understanding is that the DM spheres must have hollow cores with specific density gradients to explain flat galactic rotation curves.

Here's a quick example, using lensing to estimate galactic mass distributions.

http://www.control.com.au/bi2003/articles241/feat3_241.shtml

The cold dark matter theory predicts that dark matter should clump together in the centre of galaxies and dominate the galactic centre. In the galaxy we studied, however, the dark matter plays an insignificant role in its centre, accounting for less than 4% of the mass within the gravitationally lensed images. Instead the mass here is dominated by the stars in the bulge of the galaxy.

The dark matter does play a very large role in the overall galaxy, contributing about 60% of the total mass within the radius of the visible light of the galaxy, but its contribution is primarily to the outer regions. Other work has suggested a similar distribution of dark matter in other galaxies, but this is the first galaxy to be used that definitively discredits the current theory.

From the same authors:

http://e-collection.ethbib.ethz.ch/ecol-pool/poster/poster_18.pdf

 

[Garth]

6) The Matter Density

The matter density is, quite simply, the average space density of matter in the universe. It is usually parameterized relative to the critical density:

\Omega_m=\frac{\rho_m}{\rho_c}

This is the density of all non-relativistic matter, including the stuff we're made of (baryonic matter) and the dark matter that has so far eluded our detectors. It does not include photons, relativistic particles, or dark energy.

Since it includes the stuff we can't see, the estimates of \Omega_m must be dynamical; that is, they must be inferred from gravitational influence of the matter. Doing this in a variety of systems (on both small and large scales), we can directly measure the total amount of matter in the universe. These methods tend to give values in the range:

\Omega_m \sim 0.2 - 0.3

Remember that \Omega_m=1 would mean that the matter density was exactly sufficient to flatten the universe. Recently, several other independent measurements, including the peculiar velocity field of galaxies, the power spectrum, and the CMB, have given values that are in the same ballpark. In fact, measurements of the matter density have been confirmed in so many different ways that it was previously believed that we lived in an open universe with \Omega\simeq \Omega_m \simeq 0.3. With the recent CMB and supernovae measurements, however, we now believe that the remainder of the energy density required to flatten the universe is in some other form, this mysterious dark energy.

Thank you for these clear contributions ST; is it not correct to say that the CMB data is also consistent with conformally flat space?

Garth