a-cosmology-group/acg#235

I had been interpreting it as the wider light curves were that way because of time dilation, which is the same 1+z as redshift. It looks like the wider ones would be at a higher z and also have the brighter magnitudes. But it seems I’m interpreting it wrong, and this is just natural variation in type Ia SNe.

@mikehelland the curves you posted above show that “wider light curves” correspond to “more luminous supernovae”, this is just a natural property of SNe observed at very low redshifts. (Not to be confused with time dilation.)

Layman but SALT2 correct for color reddening with distance and for the stretch factor which are two independent biases that cause scatter and broadening. Crawford has however shown that there are issues with using SALT2 for time dilation analysis. Btw thanks a lot for making open source notebooks 🙏

I am well aware of this study, I did not mention it previously because it complexify the topic of reproducing cosmic time dilation tests. https://arxiv.org/abs/2406.05050 There are many things that are wrong with this study..

1. they use SALT3 which has major deficiencies The state of the art study on ZTF DR2 conclude:

SALT3, with its version 2.0, show significantly more lightcurve residual deviations than SALT2 (T21 or 2.4-JLA), and should then not be favored for precision cosmology prior updates fixing these issues.

We thus conclude that SALT3 is very similar to SALT2 in describing the ZTF lightcurve data. SALT3 seems slightly better at describing the second-peak epoch but does significantly worse pre-maximum light, indicating that future trainings should reduce the degree of regularization applied. Altogether, we encourage to wait for a future SALT3 version prior using it for precision cosmology, thought the current implementation has been shown to resolve other issues relevant to cosmology as compared to SALT2 (see details in Taylor et al., 2023). https://arxiv.org/html/2406.02073v1#S6

Secondly they appear to do complete circular reasoning (they literally add a time dilation signal) thirdly they don’t reproduce crawford study meaning we don’t know wether it is actually the dataset that is being tested or merely a product of their potentially contrived analysis methodology. See the Figure C1 in the DES study: https://arxiv.org/abs/2406.05050 Does it look like time dilation to you? It looks like absolutely the opposite, the very small increase being driven by the well known dust reddening bias and stretch factor. Not a single dot on the time dilation predicted curve, very far from it. I understand the topic is more complex than I can appreciate but I’m pretty sure they haven’t factored in the SALT2 biases Crawford outlined either and have made an expandist model dependent analysis. Again @mikehelland I strongly hope you will do an analysis yourself (firstly by reproducing Crawford paper in a jupiter notebook then via testing on DES and on the highest Z supernovaes (Z=2.9)). Few people know it is also possible to test on golden samples with considerably reduced intrinsic scatter, either via a sibling golden sample https://arxiv.org/abs/2406.01434 (50% scatter reduction) or via taking into account the supernovae distance from its galactic center (the farther from the center, leads to a 30% reduction in scatter (signal to noise)) (which is most likely an effect of dust density).

The proper methodology is: https://arxiv.org/abs/1711.11237 Note that the DES dataset is an improvement because it has a higher percentage of “high” Z supernovaes (up to Z=1.1)

As for the figure C1

If there was no time dilation, these fits would be horizontal lines with b=0.

Firstly I strongly disagree, a minor deviation from the horizontal line is simply the effect of some unaccounted color or stretch bias. Any dot below the diagonal line is consistent with no time dilation. Moreover even by their own account they utterly fail (scientific fraud?) to note that the blue line perfectly align with the horizontal line for the red light curve of the “g r i z” Hence perfectly consistent with no time dilation. The I line fit is very close to the horizontal line. As for the g the signal is below the horizontal line, I don’t understand its Semantic or what would cause light contraction. Why are the points starting below 1 though those graphs are unclear as for g the bined data (red goes up) yet the blue line goes down so what is the Semantic of starting below 1.0?

The Pantheon dataset says mB is “SALT2 uncorrected brightness.” I take that to mean SALT2 was not involved in producing those values. Maybe I’m misinterpreting that. In either case, the corrected values (red dots) seems to make the uncorrected values (blue dots) less scattered. They don’t appear to change the data very significantly.

But our data points are in days, as in, how many Earth days between measurements. That seems pretty hard to “fudge”.

When I was still trying to defend tired light models I cited this paper often:

https://arxiv.org/abs/astro-ph/0404207

I think just because someone claims time dilation doesn’t exist, doesn’t really make the evidence go away. I’ll try to dig deeper into your reply to see what you’re really getting at. But it seems Crawford is in a similar boat to this Jensen fellow, intent on making the time dilation go away in order to keep tired light viable.

The challenge now will be to find an SN1a at high redshift before it hits peak brightness and watch it every night for a couple months.

I think I need a little bit more of a hint at what’s happening here, specifically SALT2. Explain like I’m 5… does SALT cause the wrong magnitudes, or wrong distances, or something else?

I take that to mean SALT2 was not involved in producing those values.

Yes the datasets (B14, pantheon+, DES 5) all provide the raw light curves without SALT2 corrections (they usually provide both). The SALT2 are usually done during the analysis of cosmic time dilation.

Note that there is no paper testing cosmic time dilation for pantheon+ albeit this dataset has less “high” redshift than DES 5.

They don’t appear to change the data very significantly.

This is not true, the SALT3 mention I cited is shown to have significant “hallucinations” SALT2 has periods (especially the start and the end) of low performance given it is outside of their training datasets as shown too in the ZTF Dr2 paper. Note that there are alternatives to SALT2 like bayeSN. I believe no curve fitter should be used. Crawford argue in depth that SALT2 removes all the cosmological information. I interpret this as a pure SALT2 analysis would show no time dilation but I am not sure as Crawford argumentation is more complex and I am bad at maths.

I was not aware of the paper you cite I shall read it.

I think just because someone claims time dilation doesn’t exist, doesn’t really make the evidence go away.

So what you consider the paper you cite merely a claim? That is irrelevant, Crawford paper(s) are not made of claims but of empirical analysises, actually until 2024 it was the largest snia time dilation analysis. https://arxiv.org/abs/1711.11237 Moreover he is the only human on this planet to have exhaustively tested supernovaes, meaning he has tested:

the raw light curves without SALT2 processing. He shows a falsification of the expandist slope at 63 sigmas for starters. The raw light curves is the most important thing to test because it bypass SALT2 removal of the cosmological information. You can see the plot of its figure 2 which completely rules out time dilation. Crawford also shows that the SALT2 templates are consistent with a static universe And also, extremely importantly, unlike the DES study, he also test the peak magnitudes (not just the widths) , which are also inconsistent with an expanding universe. (figure 3)

So Crawford analysis is clearly the most complete one in terms of the different things that are tested and made in a model independent way. On the contrary the des study do circular reasoning and inject time dilation. Indeed the question being for each Crawford analysis, does he remove the time dilation signal? The same way the des study has to be asked, do they add the time dilation signal? While the later is explicitly said, the former is unclear and beyond my competence but there is no obvious reason why Crawford asymptotic correction would bias all his different probes, including peak magnitudes.

In either cases correction are made because of dust reddening with distance that mimics a time dilation effect (red is wider than the true blue color) but this correction can be made in a good way? Via spectroscopic alignment of emission lines iirc Cf DES study, or bypassed via sibling golden sample I aforementioned or simply maybe via testing the highest redshift supernovae, which should increase the signal to noise ratio by 290%

I still have more to dig into to fully understand what you’re saying. This is getting a bit more into the weeds than I’ve been before.

But, regarding the video I posted, at 29:17 Ryan says they don’t use the SALT3 stretch parameter, but simply plot it as a consistency check.

@mikehelland

But it seems Crawford is in a similar boat to this Jensen fellow, intent on making the time dilation go away in order to keep tired light viable.

I noticed that Gupta did a study comparing numerous models on how they predict the SN light curves: https://doi.org/10.3390/universe5050102

He mentions TL models and also Crawford’s model, which he considered TL also. He writes:

Generally accepted flux loss phenomena are as follows [14]: (a) Increase in the wavelength causes the flux loss proportional to 1/(1 + z), and (b) In an expanding universe, an increase in detection time between two consecutive photons emitted from a source leads to a reduction of flux, also proportional to 1/(1 + z). Therefore, in an expanding universe the necessary flux correction required is proportional to 1/(1 + z)2, whereas in a non-expanding universe the correction required is proportional only to 1/(1 + z).

He ends up concluding that the LCDM model is the second best fit, an Einstein-deSitter model being the best. He does not mention SALT.

What I am confused about is why Crawford and @LifeIsStrange are so intent on removing the extra (1 + z) time dilation component, when that term is needed to make a good fit. On the other hand, I have read numerous times that TL models do explain the SN light curves adequately. Can you or anyone here shed light on this?

Earlier you advanced a hypothesis where time dilation is just a feature of high redshift. I think this could fit with my shell model, since the Hubble redshift then becomes a gravitational redshift due to the shell. (It’s more complicated than this, as new expressions of GR are necessary). The crazy other part is that we naturally tend to think of the gravitational redshift as not being a TL redshift. In my model, it can be. It goes back to the question of whether energy is lost by a photon in the gravitational redshift. Everyone in ACG except for me thought that it is not lost. I think that it is lost, and this lost energy is what gives rise to gravity.

Be careful here, Crawford doesn’t say that SALT2 should be interpreted as meaning “no time dilation”. In his papers Crawford writes that there is an ambiguity in the SALT2 analysis: it can be interpreted as either “there is no time dilation” (consistent with a static model) or “there is time dilation”.

Unfortunately, Crawford’s own analysis to show there is no time dilation gives incorrect results. A careful examination of his method shows that it is biased toward producing shorter light curve values. (The method is explained in arXiv:1711.11237 on p.112 in this version: Open Astronomy, vol. 26, no. 1, pp. 111–119, Dec. 2017, doi: 10.1515/astro-2017-0013.)

For a completely different method that show there is time dilation, see K. Boone et al., “The Twins Embedding of Type Ia Supernovae. I. The Diversity of Spectra at Maximum Light,” ApJ, vol. 912, no. 1, p. 70, May 2021, doi: 10.3847/1538-4357/abec3c. and K. Boone et al., “The Twins Embedding of Type Ia Supernovae. II. Improving Cosmological Distance Estimates,” ApJ, vol. 912, no. 1, p. 71, May 2021, doi: 10.3847/1538-4357/abec3b. They use the evolution of the full spectrum to give an “age” for the supernovae, without the ambiguity problems of SALT2.

(Also see my comment on Eric Lerner’s papers about citing Crawford…)

@ExpEarth. >energy is lost by a photon [ .. ] and this lost energy is what gives rise to gravity.

No. Gravity is not caused explained by electromagnetism.

Time dilation isn't a feature of high redshift. Redshifted light is time dilated light.

Time dilated light is redshifted light, but redshifted light is not necessarily time dilated. Just ask @LifeIsStrange and Crawford.

The real question is: how are you time dilating your light?

@ExpEarth. >The real question is: how are you time dilating your light?

By smaller Variable (electron) Mass $m_e$ , giving atoms with a smaller Rydberg constant. These are atomic clocks with a lower frequency (i.e vibration time dilation) and they emit redshifted electromagnetic waves.

My hypothesis is pretty ad hoc in that respect. We observe the past to be time dilated, so it is. Time was slower in the past.

The expansion model uses a changing size of the universe to do that, and Han is suggesting it’s a changing mass.

My suggestion amounts to rather than something else changing causing time to be dilated, time itself is the dynamic element of the universe.

@mikehelland I argue that it’s possible to have a static universe and dilated time, but by that I am not saying our clocks were slower in the past, but rather appear slow over a distance. Consider that the galaxies we are looking at (time dilated, red-shifted, etc.) also must be able to look at us and see the same phenomena. Yes, they see our (old) clocks as slow, but there is no rule that says we have to see our own (old) clocks as slow. In my opinion time hasn’t changed here as might be expected in a non-expanding universe. Still possible but harder to argue this for an expanding universe.

Then in a static (but self-renewable) universe time is not dilated ‘over time’, but only over distance. Just as if you’re looking into a gravity well and seeing clocks behave different. Then the redshift AND time dilation could easily be explained by a type of gravity model, such as explained by e.g. @ExpEarth model; and I also argue that it is gravity linked, but more investigation is required.

@Francois-Zinserling

Then in a static (but self-renewable) universe time is not dilated ‘over time’, but only over distance.

I had pursued that and ended up with the metric from #178 . Unfortunately, the issue with that is that we live at special place on the described manifold, so anti-Copernican, aka, geocentric.

Of course, there’s no fundamental reason the theory needs to be described with a metric and manifold the way GR does it. But I think that just raises the question, why does distance cause time dilation? Which seems to require another ad hoc hypothesis. At this point I figure, just cut out the middle men, and say the past is time dilated.

You could be right. I think the idea needs a bit more fleshing out for deeper examination. I’m not sure what the route is for doing that though.

@mikehelland

Unfortunately, the issue with that is that we live at special place on the described manifold, so anti-Copernican, aka, geocentric.

This is not so crazy as it may seem. A lot of recent evidence by Secrest and others (discussed in some other threads here) suggests that the universe is not homogeneous and isotropic. For example, quasar counts are higher in one particular direction. The CMB anomalies cannot be explained with the Milky Way velocity alone. There seems to be another directional component. The CMB temperature ‘bullseye’ distribution also points to a specific reference frame for the universe.

I have a question related to the SN curve you showed above (Pantheon-Shoes). Do you (or anyone) have a figure which shows in one graph the observed SN luminosities, the ones that the LCDM had expected to see (with their two factors of (1 + z) and the one that the TL model predicts with its (1 + z) relation? I would assume that the LCDM dark energy correction simply makes the observed values fit the LCDM expectations. But I seem to have read that the TL model also fit the observed luminosities. Is there a reference or thread that puts this all together?

Geocentrism is crazy. We’re not at the center of the universe.

As far as the data and the models, here you go:

https://mikehelland.github.io/hubbles-law/other/supernovae.htm

You can just save the page and modify it to test different models if you desire.

We can be at the center of a nearby CMB though. Moreover you are missing the point @ExpEarth makes, which is that there are diverses empirical observations, that currently points to an anisotropic universe. An anisotropic (local ?) universe is not the same thing as classical geocentrism. Without saying we are at the center of the universe, you can believe the universe has some large inhomogenous patterns, the simplest and most consistently observed one being a dipole pattern, rhoughly meaning, if I understand correctly, that the (local?) universe would have a slighly different matter concentration on its “left side” than on its “right side”, and that earth would be place in one of such anisotropy “a preferential place” or more simply an anisotropic place. The anisotropy/inhomogeineity is not necessarilly a difference in matter concentration, it could and/or be an anisotropy of magnetic force or of magnetic aligment/polarization. While the dipole phenomenon is seen in the CMB, it is independently seen in e.g. quasars, which is highly intriguing. https://arxiv.org/abs/2305.16177 Independently of that, the other most intriguing refutation of the cosmological principle is that galaxies spin directions are universally biased, in a manner potentially consistent with a rotating universe or with a distant central mass. The third observation comes from cosmic birefringence in the CMB.

The room I’m sitting in is neither homogeneous nor isotropic. The same goes for the planet, the solar system, the galaxy, and the observable universe.

But the metric I described squarely places our position as a unique position in the universe. It’s not viable.

Thanks, Mike, but I am a fish out of water on models like that. I need to see the graph where the three models are displayed.

On ‘geocentrism’, again, it’s not crazy. There is a new class of GR solutions developed by Ni, Neslusan and others which specify that a spherical distribution of liquid or gas can take the form of a spherical shell. At the centre there is a relative void of matter and a repulsive gravitational field directed outward. The Milky way is not far from the centre of the KBC Void. If that large void were positioned at the centre of the cosmic shell, then voila, we have almost that geocentric configuration. We are just off centre slightly, enough to cause the ‘dipoles’ in quasar counts, etc. The CMB temperature should drop below 2.7 K towards the very centre. This can be tested for. And SNe near the centre would have a time contraction seen at our position, also testable. From #229 :

The page I shared compares LCDM to $d_L = \frac{c}{H} (1+z) \log (1+z)$, which is what most here are using as luminosity distance in tired light. If you have a suggestion for another model to add, please state it. Otherwise, the answers you seek can by found be adjusting the parameters on that page.

eg, want to see what ΛCDM looks like without the Λ? Set ΩΛ = 0 and Ωm = 1. There’s a model with no dark energy.

Geocentrism is crazy. We’re not at the center of the universe.

Yes and no.

Agreed, no, we are not at the centre of the universe. Let’s not open that chapter again.

Yes, because no matter where you are (in the universe), you will experience a CMB and Hubble effect as if you are in the centre of your own universe. It is not unique to earth/sol/milky way. Allow for relative movement of self or background against a universal frame and get some anisotropy. This is not the same as @ExpEarth ‘centre of a black hole’ because a black hole will probably not move around with you as you travel the universe, but conceptually it relates to the same.

In the context of a metric that describes a manifold, only where r=0 on that manifold would one see the Hubble effect as we do in all directions. It describes the universe as essentially a cone, and only we live on its tip. The rest of the universe would see a very warped version of the Hubble effect. I’m not about to throw Copernicus under the bus.

We could throw the manifold idea under one though. Einstein, according to Roy Kerr, said GR is about forces, not geometry. There doesn’t need to be a GR description of the universe as a whole.

But granting that, there’s still a need for an ad hoc hypothesis. IMO, the simpler that ad hoc hypothesis is, the better.

Not sure if I follow. R=0 implies a Big Bang? But I know this is not what you mean. Every point in the universe is at the tip of their own cone, although the cone concept still leaves a taste off BB. BB breaks down, so does the cone.

In a homogeneous and isotropic space; From our perspective (with us at r=0) another point in space might look asymmetric in our manifold, but from their perspective they are at r=0 and we would appear asymmetric in theirs. So yes, it appears trying to fit everyone’s ‘universe’ into one manifold presents a challenge.

Noob question, is R the tensor scalar ratio?

@LifeIsStrange , @Francois-Zinserling . >the (local?) universe would have a slighly different matter concentration on its “left side” than on its “right side”, and that earth would be place in one of such anisotropy “a preferential place” or more simply an anisotropic place.

You might be interested in a possible explanation of the Pioneer anomaly along this line of reasoning!

The r in the metric of #178 is radius.

I agree that we can’t have us being at the tip of the Hubble ‘cone’. That would be geocentric indeed. But there are two things to consider that could put Copernicus back under the bus.

The first one, as mentioned, is that we would not be at the very centre of this GR manifold. We are just off centre. So the CMB, for example, should drop to its lowest temperature right at the centre. This would be lower than 2.7 K. This we could test for, by systematically taking measurements of CMB temperature in nearby regions in all directions .

The second one relates to the Hubble redshift of starlight. Unless we were at the tip of the cone, there would be stars nearby that should show a blueshift at our position. We don’t see any. How to explain? I argue (see #204 ) that you also have to have a photonic spacetime to account for it. The paired-photon model of Annila et al and similar to what @Francois-Zinserling describes work the best here. That photonic spacetime would have an equivalent temperature to the CMB and I argue that spacetime is in thermal equilibrium with the local CMB. Whereas CMB photons travelling from cooler to hotter spacetime regions can be blueshifted, stellar photons are always hotter than spacetime in every zone and thus are only redshifted. This is why we look like we can seem to be at the tip of the cone for starlight, but not for the CMB.

Being “just off centre” of the middle of existence is only slightly less egregious than being at the center. I don’t mean to discourage you from pursuing your model. I only simply pointed out that I had investigated a similar model, and I gave the reason for why I discarded it. Good luck.

@Francois-Zinserling . Not going to parrot your excellent replies, just notice the ❤️ emoi at some places.

@mikehelland

And I tried to explain to you how you may have been on the right track before. But here in ACG our tracks rarely meet up it seems.

On the question I had concerning whether TL models can explain the SN data, I found this recent paper by Gupta where he compares many models on SN predictions. Basically, he concluded that all of them did okay, but that LCDM and a variant of Einstein-deSitter did best: https://www.mdpi.com/2218-1997/5/5/102

Not clickable: error 404 . This is not the web page you are looking for. Clickable: Weighing Cosmological Models with SNe Ia and Gamma Ray Burst Redshift Data.

Clickable: [Weighing Cosmological Models with SNe Ia and Gamma Ray Burst Redshift Data](https://www.mdpi.com/2218-1997/5/5/102).

@mikehelland please disregard my earlier comment about discarding the cone. Somehow I had that BigBang Inflation cone in my mind while you meant light-cone. Don’t ask me how I possibly saw us at the tip of that cone! After (re)reading #178 it’s falling into place now.

@Francois-Zinserling

You’re 100% right when you say:

So yes, it appears trying to fit everyone’s ‘universe’ into one manifold presents a challenge.

The universe (manifold) would be cone shaped, and we would live on the tip. Other observers could not see the universe the way we do, which means the idea (my proposed metric) is fatally flawed.

In the June ACG Newsletter (thanks @RedshiftDrift ) there is an important article by Lopez-Corredoira et al doi: 10.1142/S0218271822501048 arXiv:2207.14688. . It’s more detailed than Gupta’s. They basically say that none of the static models can explain the data unless there is some kind of extinction (such as dust absorption), in which case they have a good probability. Some expansion models that do not work well can work if an evolution term is added. They did not consider this effect in static models, where you would normally not expect evolution anyway.

@RedshiftDrift Sorry I missed your practice talk. Good luck on Monday!

@ExpEarth . Do you ever check your links, Matt? How comes that other peoples links work and yours not?

I just use the link icon here. Maybe I should just cut and paste. Anyway, that paper is in the June newsletter.

I think you’re putting the url where the text goes. Posting a bare url without markdown auto-links.

@ExpEarth like every paper by Martin Lopez-Corredoira, this one arXiv:2207.14688 uses data analyzed in the context of LCDM to fit generic static models. That’s why the probability of a static model being correct is never as good as that for LCDM.

$\quad$ This also happened for Kepler’s elliptical orbits; at first they did not fit observations as well as Ptolemy’s epicycles. That’s because the epicycles had been adjusted to fit observations with multiple parameters.

$\quad$ Today, LCDM’s multiple parameters have been adjusted to fit observations, while static models usually have few (if any) adjustable parameters and don’t fit the data so well.

The probabilities assigned by Lopez-Corredoira are meaningless - you can’t analyze data with your feet resting in two different paradigms.

@RedshiftDrift . >you can’t analyze data with your feet resting in two different paradigms.

In thread 225 Mike Helland writes: >using the LCDM best for $H_0$ to the supernovae data is not the best fit for Hubble’s constant in a static model. The best fit (using sum of squared errors) is 70.5 km/s/Mpc.

H = 70.5 km/s/Mpc is deviant from the H = 73.4 km/s/Mpc Riess value that I have been using so far. Should I use the former or the latter value? What do you think?

The Pantheon+SH0ES data has a distance modulus in it. If you’re looking at the data by eye, it’s really hard to see any difference between models using distance modulus (because of the log10), so I convert that to luminosity distance in the standard way. But that’s only for presentation purposes.

The actual SSE calculation uses the distance modulus directly:

https://github.com/mikehelland/hubbles-law/blob/master/other/python/sse.ipynb

These values should be “model independent”.

IOW, the data has distance modulus and z. We use the z to predict a distance modulus and see how close it is to the measured distance modulus.

I think you’re suggesting use the distance modulus to predict a z, and see how close it is to the measured z. Statistically, that should be the same.

@mikehelland

Would you agree with @RedshiftDrift ’s point above that you cannot use data such as in Pantheon-Shoes to make assessments of static models? Somehow I can’t imagine that Gupta and Lopez-Corredoira could be so naive as to not realize this if true.

Also, I’m a little confused on why Gupta’s paper https://www.mdpi.com/2218-1997/5/5/102 seems to say that static tired light models are okay for SNe (see Table 1), while Lopez-Corredoira et al rule them all out, unless it’s tired light “with extinction”. I think both these papers are trying to present static model options, but the language is not clear enough for non-experts. What’s your take?

@ExpEarth

Those measurements are supposed to be model independent. The distance modulus is just $m - M$, which is apparent magnitude - Absolute magnitude. The apparent magnitude is an objective measurement that shouldn’t rely on a model. The absolute magnitude looks standardized to -19.25 on account of type Ia SNe being standard candles (there is some scatter there as shown in the second image of this comment, but I don’t think it’s all that important). The only extinction values applied here are from the Milky Way, so intergalactic extinction (which would be model dependent) doesn’t seem to be a factor.

So it should be fairly objective, but I have had some suspicions it might be skewed low, accounting for all kinds of factors that could make the SNe measurements match the LCDM+Planck value of ~67.5. Although, we can do a sanity check on that.

The predecessor to Pantheon+SH0ES is the Supernovae Cosmology Project data. Looking at them together (red P+S, blue SCP):

(Note, I again convert distance modulus to luminosity distance strictly for demonstration purposes: it’s easier to see the differences this way.)

There doesn’t seem to be anything too fishy. So I take these measurement as model independent for practical purposes. Louis’ comment is important though. Don’t go comparing LCDM values to static models. Although in this case, I don’t think it’s much of an issue, though there may be a devil somewhere in the details that I’ve missed.

Magnitude measurements should be model independent, but it’s the “data processing” done after the measurement that is model dependent.

For example, Riess compensates SNe light curves for ‘dust reddening’, which reshapes the spectrum of the SNe and has an influence on the estimated luminosity of the SN, which then adds a correction on the distance based on the corrected magnitude $m$ calculated with LCDM. It is a second-order correction, but it is model dependent. Then, Riess uses these new, slightly LCDM-biased measurements to update the SNe light curve/luminosity template, which is then used for SNe at larger redshifts.

Because all these LCDM-based corrections creep in progressively in the templates as the database gets larger, it becomes impossible to remove the LCDM assumptions unless you start from scratch. Such a re-analysis may not be too much work for Riess (with his covariance matrix containing all the data and correlated uncertainties…), but for Gupta, Lopez-Corredoira or DeBruijn that’s not really possible. They don’t have all the raw data and the software to do the analysis, so they simplify their analysis by using raw data analyzed with LCDM assumptions.

How much a difference does it make? I don’t know. But it certainly gets worse at larger redshifts. Fortunately, Riess believes his value is correct; I don’t think he corrupts his analysis with the LCDM+Planck value of ~67.5!

Agreed.

I think we’re pretty much saying the same things. The intention is for the measurements to be model independent, although if they think of something that might be a factor, they’re going to give it a try. And the measurement has gone from 74 to 73 over the last few years, which is a little closer to resolving the Hubble tension. Not that Riess and company are doing anything shifty, just following the science the best they can (regardless of what we think of their conclusions).

IOW, the measurements are supposed to be model independent. Some skepticism is warranted though.

Thanks @mikehelland and @RedshiftDrift . So, to try to sum up, the efforts by Gupta and Lopez-Corredoira may inadvertently have an LCDM ‘contamination’ that could affect their analyses and there is nothing they can do to improve matters. I notice that both of them give LCDM the highest or second highest probability, which itself suggests possible circularity.

Supposing the contamination to be small, it seems that the models most closely fit the data if there is some factor that reduces the flux received from the distant SNe beyond expected values. For static models, the fit seems worse than expanding models, as there is one less factor of (1 + z) assumed. The SNe will all appear too faint. Before dark energy was introduced, even expansion models with their two factors of (1 + z) resulted in SNe being too faint. That’s why they added dark energy. The Lopez-Corredoira study allows some expanding or TL models to fit if extinction or evolutionary effects are added. The extinction here refers to intragalactic and intergalactic dust. The dust is removing flux. The evolutionary models feature (I think) the idea that SNe were intrinsically dimmer in the ‘early universe’. (I would think the JWST observations would argue the other way.)

I think to really get a TL or static model to fit, you need to first add the extra factor of (1 + z) somehow. In my present model, if the Hubble redshift is a gravitational redshift, that could give the extra factor with gravitational time dilation added. But even that is not enough. What I suspect is happening is that the Hubble constant is not uniform with distance. This is due to the shell morphology I am proposing. It’s 74 or so here, but out there it drops to the Planck value 67 or so. This will make distant objects appear more distant (and fainter) than they really are.

My take away is this. LCDM with its six parameters is the best fit for SNe data at 73 km/s/Mpc.

But that’s inconsistent with it’s own predictions of H0 from the CMB ala Planck. So who cares?

TL models also suffer from the Hubble tension. You might discard it by believing the CMB is non primordial but then you have the coincidence problems of why parameters derived from the CMB works so well. I lack expertise but my tentative guess is that the only information being used in the CMB is the sound distance which just so happen to give the same Hubble constant value via BAO data of galactic clusters. Hence if so, the CMB usefulness would just stem from being a proxy of BAO data, the sound horizon scale, via maybe the cluster inprint through the SZ effect? If my understanding is correct then the real tension is not one of the CMB with late universe probes, but a tension between BAO (roughly the shape/velocity/spacing of clusters) and with other probes. Either the hubble constant truly is different at cluster scales (hence not an early VS late universe perspective as often purported but a scale dependent acceleration), either there are new physics in clusters/BAO scales (maybe related to the unexpectedly high ellipticities of galactic groups) or systematics/biases. I’d add that few people know that while static universes won the alcock paczynski test with eBOSS, the DESI data is currently falsifying both static universes and RH=ct, which is a gigantic issue albeit DR2 should give us a more definitive answer.

On a related topic, there is the debate of 3D vs 2D Bao data, which I don’t understand well.

On a pedantic note I’d consider LCDM having 7 parameters given fixing the universe curvature is currently absurd given its preference by multiple datasets. On an even more pedantic note, it seems one parameter can be in principle derived from the others https://arxiv.org/abs/2405.13680

TL models also suffer from the Hubble tension.

How so?

I already said about the coincidence problems of the extreme success of cosmological parameters derived from the CMB. Even if you forget about the CMB, BAO data from clusters (via e.g. DESI) derive a hubble constant in tensions with other probes (supernovae, etc) This tension affects tired light and rh=ct because they too have to explain BAO cluster measurements.

Huh. I’m not sure that’s something a human would say.

How would you summarize the Hubble tension?

I’d don’t think it’s possible to phrase it more simply than I said, the hubble tension is simply a discordant measurement of the hubble constant between two methods (probe). Since all methods agree on the same value except the BAO probe which is a cosmological test made on galaxy clusters, there is a tension. This tension must be explained in any cosmology, whether static/tired light or LCDM. https://en.m.wikipedia.org/wiki/Baryon_acoustic_oscillations

If tired light happened to be the right explanation, none of the CMB/BAO measurements would have any relevance to cosmology or the Hubble constant. There would be no Hubble tension.

This is not true, the shape and spacing of galactic clusters is cosmology dependent, not only must a TL theory match observed clusters parameters, the derived hubble constant must also match the value derived from other probes. Cluster cosmology is meaningful beyond LCDM even though the concept of BAO is often explained as a primordial big bang phenomena, which it actually doesn’t need to be. http://astro.vaporia.com/start/alcockpaczynskieffect.html The AP test is one of the very few proper test of cosmological models along with tolman and distance duality tests.

@mikehelland I would be more affirmative: tired light is the right explanation, none of the CMB/BAO measurements have any relevance to cosmology or the Hubble constant. There is no Hubble tension. (Of course one has to remove LCDM ‘contamination’ and use the correct TL model; Lopez-Corredoira doesn’t.)

The CMB measurements would still be important at least with respect to the CMB temperature-redshift relation. I’m not sure how the CMB/BAO would relate to static models. From the Wiki page on BAOs it seems the BAOs are rooted in Big Bang assumptions. I’d say a Hubble tension could still be possible.

@RedshiftDrift this is wrong and a popular myth. See my comment above, BAO doesn’t need to be primordial. The Alcock Paczyinski test is one of the most important cosmological tests and apply for all cosmologies, including static/tired light universes. The hubble tension exists independently of the CMB as it truly is a tension of cluster measurements with supernovae measurements.

You can see for example from this BOSS BAO study conducing the AP test:

Only two of the six models above fit the data of the Alcock & Paczynski test: concordance Lambda-CDM and static universe with tired-light redshift; whereas the rest of them are excluded at a >95% confidence level. https://arxiv.org/abs/1312.0003

these (BAO) peaks could be generated with other cosmological assumptions different from the standard interpretation of acoustic peaks (L´opez-Corredoira & Gabrielli 2013) https://www.prophy.science/article/711920/

The paper [2] will argue that a power spectrum with oscillations is a rather normal characteristic ex￾pected from any fluid with clouds of overdensities that emit/absorb radiation or interact gravitationally with the photons, and with a finite range of sizes and distances for those clouds. It will also show that the angular correlation function can be fitted by a generic function with a total of ≈ 6 free parame￾ters. The standard cosmological interpretation of “acoustic” peaks is just a particular case; peaks in the power spectrum might be generated in scenarios that have nothing to do with oscillations due to gravitational compression in a fluid.

The baryonic acoustic oscillations come from some quantumy stuff happening right as inflation kicks in. I’m at a bit of a loss in comprehending what it could possibly refer to outside of that context. The AP test is news to me. Can you explain what’s actually being measured and how it relates to non-big bang cosmologies?

Edit: I guess it’s not related to inflation. I was thinking that was the cause of the “freeze”, but it’s just regular expansion.

Indeed BAOs stems from quantumy stuff in the standard model and in some possible alternative cosmologies. One has to wonder even in alternative cosmologies, what is the source of variety/diversity in the universe? Any deterministic law/cellular automata should cyclically reproduce the same pattern over and over, beyond a certain distance. Despite being seemingly isotropic and homogenous, each individual galaxy and their components seems quite unique (even though we can roughly classify them by their shapes) Of course Chaos theory shows that even with classical physics, a dynamical system can in some cases generate extreme diversity. Still it is an open question whether there were at the start of the universe (assuming there was a start), primordial sources of randomness that could explain such diversity. Aka quantumy stuff. Regardless of that point, Cf the paragraph I cited, it appears BAO are a normal phenomena to be expected in any cosmology assuming the universe has periodic large scale variations in matter or radiation densities.

While I have read enough of the literature to know the AP test is fundamental and apply for all cosmologies (and allows to derive record constraints on LCDM parameters), I do not understand precisely how the test is performed in practice. Like almost all cosmological tests, e.g tolman or distance duality, it seems to leverage the fact that the diverse measures of distances evolve differently in a static versus an expanding universe. Basically while both cosmologies have roughly the same Redshift distances (hubble diagram), their luminosity distances and angular distances scale differently (e.g. At high distances objects appears larger in an expanding universe because of an optical lens effect) The issues with both tolman and distance duality tests is that they depend on luminosity uncertainties (can be improved via UV max surface brightness) and they depend on astrophysical evolutions of objects (stars, etc) and properties of dust obscuration. Because the AP tests is applied on large scale structures such as galactic clusters, it is largely independent of evolution and other sources of uncertainties.

Here are some explanations of the test I could find:

AP is an evaluation of the ratio of observed angular size to radial/redshift size. The main advantage of this test is that it does not depend on the evolution of the galaxies but only on the geometry of the universe. However, the redshift distortions produced by the peculiar velocities of the gravitational infall also have an influence, which should be separated from the cosmological effect.

Or as said by the original inventors:

The test involves the evaluation of the ratio between the differences in the redshifts of an expanding spherically symmetric distribution of radiation-emitting objects and the product of their distance with the angular radius of their distribution on the sky assuming a homogeneous, isotropic cosmology https://ui.adsabs.harvard.edu/abs/1979Natur.281..358A/abstract Equations can be found here https://ned.ipac.caltech.edu/level5/March14/Percival/Percival5.html

So without understanding precisely, it seems the AP test rely on those well known distinct distances evolutions between cosmologies, and more specifically, it is expected that large clusters are on average spherically symmetric, the AP tests seems to shows that if a cosmology gets angular distance and redshift wrong versus empirical observations, it will shows as a distortion (non spherical) in the calculated shape of clusters.

Now the big question to me is how does this relates exactly to BAO? I don’t know but it is a fact BAO datas are what is used for performing the AP test. For some reason I don’t understand it appears they extract the redshift and angular size information of clusters from BAOs, or that they disentangle the RSD (redshift spectral distortions noise) via BAOs. If you want a proper precise answer you could ask Lopez or Fluvio Melia. The RSD are also interesting and will allow to derive strong cosmological constraints in upcoming sky surveys.

The information is hidden in the DESI DR1 paper but DESI AP test falsify static universes while previous BOSS dataset prefered static universes. Now there are some issues with DR1 so there are still hopes for DR2 but while cosmologists on this forum since to ignore the existence the AP test, it is the viability of our cosmologies that is at play here and this matters even more than the related Hubble tension. Thankfully we will soon have other large BAO datasets than DESI, especially from Euclid in both optical and infrared but also from radio waves via SKA and others. Moreover it is often underappreciated that the AP test apply on any spherically symmetric large scale structure, meaning that while most surveys rely on BAO/cluster data, it is becoming possible and competitive to perform the AP test on cosmic voids. https://arxiv.org/abs/2407.02699

There is only ‘one Hubble tension’. The uncertainty on TRGB measurement is too large to conclude it is in tension with the other probes.