Critique of Mainstream Cosmology

Garth

Hopeful signs of the Pioneer Anomaly: Evaluating Newly Recovered Data.
It sounds as if they have some way to go before any results from this study ......

Garth

oldman

I seem to have inadvertently diverted this thread away from its main thrust, which was

The discussion so far has been concerned largely with Lieu's paper (which includes much special pleading) and with the puzzling Pioneer anomaly. But it is clear that apart from disturbing Lieu, many of the knowledgable folk who post in this forum and accept the consensus LCDM model do so only as a working hypothesis, sometimes reluctantly and for various reasons. For instance, I notice that Marcus joins that august publication, The Economist, in labelling LCDM a kludge:

I suggest that when rectifying kludges it is often useful to go back to the very beginning and re-examine the fundamentals. In this vein GR is a target for Marcus, and for Garth, who prefers the alternative of his Self-Creation cosmology.

I'm an outsider who finds the description of gravity given by GR convincing, at least as a working model. But perhaps there are alternatives to modifying GR. Take the founding
observation of modern cosmology, the redshift, which Lieu mis-spells in his Table 2 and attributes simply to "the expansion of space", whatever this is. (Note that some deny that space expands, some find "space" a convenient didactic fiction, while others -- like myself -- are mystified by the very concept of space. See several threads in these forums.)

What if the founding observation of the redshift has been misinterpreted in the context of a correct theory, namely GR?

Remember that astronomers have long been accustomed to measuring spectral shifts to determine, say, the radial velocities of stars and rotation speeds of galaxies. This is the context in which the redshift was discovered and interpreted. It was therefore natural, in the R-W metric, to account for the redshift with a scale factor that serves as a common multiplier for the metric coefficients of the space dimensions. This preserved the link to the then-prevalent Doppler-shift wisdom about spectral shifts. So much for how the founding notion of isotropic expansion became embedded in cosmological thinking some eighty years ago.

But the cosmological redshift is sharply distinguished from all other astronomical spectral shifts by its symmetry, which is seldom explicitly considered. Perhaps this special feature tells us that the R-W metric is universal. Or perhaps it tells us that something like the symmetric laws of perspective are involved. Or there may be alternative ways of incorporating this symmetry in GR, without throwing the entire LCDM model out with the bathwater, as it were.

How do contributers to this thread view the symmetry of the redshift? Too simple to discuss?

turbo

Redshift is fundamental, and perhaps is in need of epistemological treatment. Hubble never bought into the notion that redshift had to arise from recessional velocity, despite the often-repeated statements that he "discovered" universal expansion. That view was promoted by physicists (Eddington, Le Maitre, De Sitter, etc) as opposed to observational astronomers. Fritz Zwicky's view of redshift was that of "tired light" - light that has lost energy while on its journey to our detectors. This idea has been out of favor for a long time, although it may make a resurgence. Several years ago, Fotini Markopoulou of the Perimeter Institute posited that light must lose energy through its interaction with the space through which it propagates. She reasoned that light of short wavelength must interact more frequently with space than light of longer wavelengths, and its arrival time would therefor be delayed. She speculated that GLAST would demonstrate this by observing a gap between the arrival times of gamma rays and longer-wavelength EM. As it stands presently, the MAGIC consortium may have trumped GLAST by recording a delay of about 4 minutes in the arrival times of high-energy EM. This result needs to be confirmed and duplicated with other observations. If indeed similar delays are observed in high-energy bursts from other sources, and the delays prove to be proportional to the redshifts of the sources, "tired light" may once again join the lexicon.

Garth

The general observation of cosmological red-shift serves to confirm the expanding universe model and is therefore not a candidate for discussion in this Thread.

If there are any specific red-shift observations that question the standard [itex]\Lambda[/itex]CDM model, such as high red-shift objects that appear older than the universe at that red-shift, then they would be appropriate to discuss here.

Opinions of how the observed red shift may be interpreted will make a valid discussion in another thread. Unless there is a published theory that makes such an interpretation, and the Jordan Frame of Self Creation Cosmology would be one example of such, claims for alternative interpretations will have to continue on the Independent Research Forum, of course after observing their Rules for Submission.

It is not up to me, but I would think it all right to pose intelligently framed questions about the standard model in this Forum, but in another thread please.

BTW turbo-1 I have already given one explanation for the 4-minute delay in post #6 of this thread.

Garth

turbo

So noted, Garth. Additional observations are required, as I said, and as you said it may turn out that there is a mundane explanation for the observed delay. There are some rather stringent requirements that must be met for the MAGIC result to stand, including the correlation of frequency-dependent delay and the redshift of the source.

As for high-redshift objects that appear too old to be viable at their redshifts, one only need refer to the papers of Fan, Strauss, et al of the SDSS consortium. They have discovered quasars at redshifts up to ~6.5, and if the quasars are truly at the distances implied by a standard interpretation of their redshifts, they would have to be comprised of BHs of perhaps 10 billion solar masses, residing in host galaxies of about a trillion solar masses. In addition, these quasars show no evolution in their absolute metallicities or relative metallicities, despite the fact that the various metals comprising them are thought to arise through processes that are currently believed to be time-dependent. As Strauss notes, theorists have not been able to explain how such massive, highly-metallized objects could have formed only a few hundred million years after the BB. His presentation to the STSCI is the 6th on this page. It is very informative, and I highly recommend watching it if you have the bandwidth to stream it, or can download it overnight.

http://www.stsci.edu/institute/itsd/...oquiaFall2005/

Garth

Indeed, unambiguous observations of high red-shift SMBH's could bring into question the expansion history of the standard model.

One of Michael Strauss (Princeton) conclusions from the SDSS survey: Active Galaxies at Low and High Redshift: Type II Quasars, Reionization, and Other Insights from the Sloan Digital Sky Survey These are around z > 6 when the universe was less than 1Gyr old.

Theorists of the standard model have their work cut out to explain the formation of the large BHs required to power such quasars at those early times. For example: SDSS J1148+5251: a hyperluminous high metallicity galaxy, in the early universe
Garth

Chronos

More data, less theory is suggested. While existing data is not irrefutable, the odds increasingly disfavor Arpian interpretations.

Garth

I wasn't suggesting Aarp, just a modification to R(t) at high z.

Is it possible the standard model equation of state for (DE + matter) is incorrect?

Garth

jonmtkisco

Hi folks,

The best critique of mainstream cosmology I've read is "Endless Universe: Beyond the Big Bang" by Paul J. Steinhardt and Neil Turok. It was published at the end of May this year. Steinhardt was one of the pioneers who helped shape current inflation theory.

The authors of this book rip current inflation theory into many tiny pieces. They think it is full of inconsistencies and unjustified assumptions. Their alternative theory involving the "M Theory" and branes leaves me cold, because I have no basis to know whether it makes any sense at all. It sounds a bit goofy to me. They say that further analysis of the WMAP CMB data may clearly identify whether their theory is more likely than inflation. With the WMAP data released so far (including the May installment) they consider it to be a temporary tie. In any event, it is thrilling to see mainstream inflation theory demolished in a very logical manner by insiders.

Can there be any such thing as "accepted mainstream cosmology" when the best minds in the discipline disagree with each other so strenuously? If inflation ultimately is invalidated as a theory, cosmology will have a lot of backpedaling to do. But of course it's too early to tell, and a great many cosmologists undoubtedly think these authors are barking up the wrong tree.

Jon

SpaceTiger

Not really. The reason inflation is still so controversial is that it's so hard to test experimentally -- inflationary models can explain almost anything. If it turned out that Steinhardt's theory was right, it would would be of little consequence to most cosmologists because both theories predict the same thing in the regimes they're concerned with. LCDM itself doesn't actually rely on inflation.

Garth

S.T. I am mystified by this statement.

Is not Inflation necessary to resolve the density, smoothness and horizon problems of the decelerating universe in that early stage of the [itex]\Lambda[/itex]CDM model?

Garth

oldman

 If the LCDM consensus is so limited as to not necessarily include infation, as Space Tiger seems to imply in the above quote, then the observation that opposite sides of the sky are similar falls back into the category of observations to be discussed here. Perhaps you should clarify the intended purpose of this thread, Garth, before it runs away.

Garth

As I have said this thread is to discuss observations that may call the standard [itex]\Lambda[/itex]CDM model into question.

As far as the horizon problem is concerned, arising from the observation that "opposite sides of the sky are similar", I await S.T.'s answer to my question about his statement.

To my way of thinking you are right, if Inflation is not part of the standard [itex]\Lambda[/itex]CDM model then that observation would question that model.

The horizon problem arises because in a decelerating universe, disparate parts of the present sky would have been beyond their mutual casual horizons in the earliest stages of the BB. The standard [itex]\Lambda[/itex]CDM is decelerating for most of its expansion history, DE acceleration only 'kicking' in since z ~ 1 or so.

Garth

SpaceTiger

Yes and no. Yes, these are conceptual problems with the mainstream cosmological model that are not resolved without inflation. However, inflation is primarily a tack-on. What I normally understand to be [itex]\Lambda CDM[/itex] (and this is merely a matter of convention) is the general relativistic model of the expansion that occurs after the end of the inflationary period. This is the part that most observational projects rely on and this is the part that has been tested to the most precision. All we need for the majority of cosmological studies is to know that the universe is flat and that the initial power spectrum of perturbations is nearly scale-invariant. The theory that explains these facts is irrelevant for most purposes.

I'm not sure to what extent the community separates inflation and LCDM, but my point is that it's an easy separation to make. Disproving inflation does not invalidate the work of people working outside of inflationary theory. By contrast, if it were found, for example, that the interpretation of redshift as expansion were incorrect, then there would have to be major revision of almost everything cosmological from the last 30 or 40 years.

SpaceTiger

It's not clear to me why. If LCDM is not claiming to explain the origin of fluctuations, why would a problem concerning the initial distribution of those fluctuations bring it into question?

SpaceTiger

Actually, I think questioning inflation is an excellent choice of topic for this thread, as the theory seems to have settled into the mainstream without being rigorously tested. It certainly isn't inconsistent with the observations so far, but things like the flatness problem, the horizon problem, the monopole problem, etc. should not be considered evidence (IMO) because the theory was designed to solve those problems.

Garth

In GR, a decelerating universe raises a series of questions: the horizon problem (why are opposite sides of the sky similar when they are casually unconnected?), the smoothness problem (Why are the fluctuations ~ 10^-5 just right to produce a universe with large scale structure and galaxies etc. yet not too great so all matter clumps together in a few hyper-massive BHs?), the density problem (Why is [itex]\Omega_{total}[/itex] ~ 1?), which can only be answered by special pleading - i.e. by setting specific initial conditions that can perhaps only be explained by Anthropic reasoning.

Another answer is of course that the universe may not have been decelerating over most of its history. [Apart from the Inflation era: 10^-35 sec to 10^-33 sec, according to the mainstream model the universe has been decelerating from the Planck era t = 10^-43 sec to t > 10⁺¹⁷ sec, when DE acceleration kicked in. The present age t ~ 4 x10⁺¹⁷ sec.]

The monopole problem is different in that it arises from the GUT, which predicts magnetic monopoles should be plentiful and detectable. A lack of their detection therefore requires an explanation, such as Inflation, which would have diluted their density to undetectable levels.

Another explanation is of course that the GUT is wrong and they never existed in the first place.

Inflation resolves these problems by injecting massive expansion at that early yet post-Planck era stage, which more than counteracts the effects of the subsequent deceleration. Without it the standard model has some explaining to do.

One resolution would be to have an unorthodox equation of state for DE in order to have an extended era of acceleration, i.e. a kind of 'smeared out' inflation, or indeed a strictly linear expansion , but that is definitely 'non-standard'!

Garth