Hubble tension -- any resolution?

[Mordred]

TL;DR

Hubble tension any resolution ?

A few years back there was an issue called the Hubble tension where the observations were nor matching up to predictions when looking at the Early and late time data.

I had heard that one possible explanation is due to our being in an underdense region but have also read a counter paper to this.
Has there been any resolution or is the issue still being resolved ?

 

[Vanadium 50]

Well, I guess that depends on what you mean by "a few".

Maybe 30 years ago, the Hubble tension was whether it was around 50 km/s/Mpc or 100. Today the tension is whether it is around 68 or 74.

 

[Bandersnatch]

Has there been any resolution or is the issue still being resolved ?

Still unresolved, it seems. The latest voice on this was from the DESI collaboration:

Fig. 9 from data release VI ('Cosmological constraints...').

 

[PeterDonis]

Maybe 30 years ago, the Hubble tension was whether it was around 50 km/s/Mpc or 100. Today the tension is whether it is around 68 or 74.

But the source of the "tension" now is not quite the same. Maybe 30 years ago, the "tension" was just due to relatively large error bars on the various measurements that go into estimating the Hubble constant, so the range of possible estimated values was pretty wide. Now the "tension" is that there are two different calculations based on two different sets of measurements and they give different answers, and at least according to some, the error bars around each calculation are narrow enough that the difference between the two answers is significant.

 

[Mordred]

Still unresolved, it seems. The latest voice on this was from the DESI collaboration:
View attachment 346355
Fig. 9 from data release VI ('Cosmological constraints...').

Thanks Bandersnatch for that reference. Guess it's a problem that's going to take some time to pin down. Not that I expected an immediate resolution given the nature of the problem and the difficulties that go with precise measurements at different cosmological scales

Just to avoid confusion this is the tension I'm referring to

Tensions between the Early and the Late Universe​

https://arxiv.org/abs/1907.10625

 

[PeterDonis]

this is the tension I'm referring to

This is the tension I described in the latter part of post #4.

 

[Vanadium 50]

Maybe 30 years ago, the "tension" was just due to relatively large error bars on the various measurements that go into estimating the Hubble constant,

Just the opposite. The error bars were too small.

I'm told that it is totally impossible for that to be the case today. Of course, U was also told the exact same thing back then.

 

[PeterDonis]

The error bars were too small.

I thought the error bars back then were large enough that the range of estimates was 50 to 100.

 

[Mordred]

yes I caught that reference in post 4. It brought me to thinking I should include a reference for any other readers who may not be familiar with the tension.

I often keep wondering if the tension may have something to do with how the evolution of matter and radiation vary due to expansion via the following relations as a function of redshift

$$ H_z=H_o\sqrt{\Omega_m(1+z)^3+\Omega_{rad}(1+z)^4+\Omega_{\Lambda}} $$

another conjecture I thought of trying is to look into the Saha equations for any phase transitions that may apply but those are just conjectures on my part. ( I would be surprised if these haven't been looked into where applicable )Though I am currently researching electroweak and nucleosynthesis processes I doubt it will affect what I'm working on. So its more for curiosity sake on any new findings in regards to the tension

 

[Bandersnatch]

Just the opposite. The error bars were too small.

Can you provide a reference? What different measurements were in tension back then?

 

[Vanadium 50]

I'll look things up when I gey a moment (which will nit be today and probabkt not tomorrow). Looking up decades old papers is not as easy as looking up years olds paper.

 

[Mordred]

I do recall some contention with the first Planck dataset with its low value of (if I recall correctly 67) when previous datasets were roughly 73 ) .

It seems to me Planck always had a lower value than other datasets such as from COBE and WMAP as two examples. Thinking about this last night made me realize there is one question I don't know how to answer.

What happens to expansion rates as a result of recombination when the mean average density of protons/neutrons and electrons combine to form atoms ?

Yes they would all have the same equation of state (matter P=0) . However the density change should effect expansion rates. I dont recall ever reading any literature describing this effect on expansion rates.

 

[Bandersnatch]

However the density change should effect expansion rates.

Why would matter density change on recombination?

 

[Jaime Rudas]

But the source of the "tension" now is not quite the same. Maybe 30 years ago, the "tension" was just due to relatively large error bars on the various measurements that go into estimating the Hubble constant, so the range of possible estimated values was pretty wide. Now the "tension" is that there are two different calculations based on two different sets of measurements and they give different answers, and at least according to some, the error bars around each calculation are narrow enough that the difference between the two answers is significant.

Yes, it is called "tension" when the error bars narrow to the point where they no longer overlap. What was happening 24 years ago was not a "tension" because the error bars were too wide: from 64 to 80 km/s/Mpc.

In fact, the Hubble tension began with the first Planck measurements in 2013, which gave Ho=67.3±1.2 km/s/Mpc, while cosmic distance ladder measurements gave 74.5±3.0 km/s/Mpc, as can be seen in Figure 6 of https://arxiv.org/pdf/2308.02474

Regarding the OP's question, it seems that in a recent conference, Wendy Freedman showed signs of a possible solution, as described by Dr. Becky here.

Of course, as Dr. Becky rightly points out, we need to wait for the publication of the paper to draw conclusions.

 

[Jaime Rudas]

I often keep wondering if the tension may have something to do with how the evolution of matter and radiation vary due to expansion via the following relations as a function of redshift

$$ H_z=H_o\sqrt{\Omega_m(1+z)^3+\Omega_{rad}(1+z)^4+\Omega_{\Lambda}} $$

Well, that's what Adam Riess has been hinting at for at least 5 years: that there is something wrong with the Standard Model and therefore new physics is required to solve the Hubble tension.

 

[Mordred]

Why would matter density change on recombination?

That's the conjecture I'm not positive that recombination would or wouldn't alter the overall matter density. Matter doesn't have a momentum term to exert pressure (not that pressure is particularly applicable ) it may be that the reason I've never come across any particular literature involving a change in matter density is that no change in the density occurs due to recombination. However I don't know that for sure. You could very well be correct that no change occurs in so far as the critical to actual density relations via the critical density formula.

 

[Mordred]

Thanks for that link will look at it after work Jaime

 

[PeterDonis]

no change in the density occurs due to recombination

No change in total stress-energy density occurs, but there is a change in the matter density, because the binding energy of recombination, which before was contained in the matter (nuclei and electrons), gets released as radiation. So some of the total stress-energy density gets changed from matter density to radiation density.

Why would matter density change on recombination?

See above.

 

[Mordred]

Thanks PeterDonis that makes sense. Lol though now I want to look into the applicable calculations lol. Thankfully I already have the calculations for hydrogen deuterium and lithium via the Saha equations or rather the applicable graphs

 

[Bandersnatch]

because the binding energy of recombination

Yeah, I thought that might be the idea. But while technically true, that's gotta be negligible for any purposes concerning evolution of the universe. We're not even talking nuclear binding energies here.
Which, imo, would be the likely reason Mordred's never saw it included anywhere.

 

[Jaime Rudas]

What happens to expansion rates as a result of recombination when the mean average density of protons/neutrons and electrons combine to form atoms ?

Given that the CMB is the result of recombination, I don't think this can be related to the Hubble tension.

 

[PeterDonis]

while technically true, that's gotta be negligible for any purposes concerning evolution of the universe.

Yes, the binding energy as a fraction of the total is very small--about one hundred millionth if we assume hydrogen-1 (about 10 eV binding energy vs. about 1 GeV total energy per hydrogen atom).

 

[Mordred]

Thanks then I don't need to consider it for my project regarding nucleosynthesis. Though that's one portion of the project ( the tail end so to speak). Regardless that is a bit off topic as mentioned it should have no significant effect on expansion rates my thanks on that.

 

[ohwilleke]

I'm told that it is totally impossible for that to be the case today. Of course, U was also told the exact same thing back then.

The statistical errors in the data, and the identified systemic measurement errors, are probably too small, even if slightly understated, to resolve the problem.

The late time Hubble constant estimates have moderately large errors amenable to slight adjustment, but the Planck CMB based calculation has such a large data set and involves such precise observations, that at least within the model within which the calculation is done, the errors are tiny. And, the tension is too big to resolve with errors in the late time Hubble constant measurements alone. It also makes sense to doubt that the late time measurements are really the problem, because, while they have larger error bars, these measurements are also robust, with many different methods of measuring the Hubble constant in the late time era largely confirming each other.

Many preprints by independent authors so far this year have all reached that conclusion. See, e.g., Kumar (2024), Gialamas (2024), Colgáin (2024), Roy (2024), Pogosian (2024), He (2024), Calderon (2024), Signorini (2024), and Akarsu (2024). Valentino and Blunt have even written a whole book on the Hubble tension, largely concurring with this conclusion.

Stacy McGaugh speculates that the problem may be "a systematic in the interpretation of the CMB data rather than in the local distance scale."

In other words, the tension might be a modeling error in the CMB based calculation of the Hubble constant, since that is a model dependent calculation and there are other cracks in the LambdaCDM model of cosmology that was used to make that calculation (such as the appearance of galaxies observed by the JWST sooner than the model). See also Liu (2024) making a similar analysis. (Note that in the sense being discussed, the argument being made is not that "modeling error" means that the LambdaCDM model was inaccurately translated into math and data analysis by Planck's scientists; instead, the concern is that the LambdaCDM model is not the correct cosmology model to use because it misstates the astrophysical reality.)

This makes sense, because inaccuracies in the model used to make the calculation won't show up in the Planck measurement error bars, and because this is pretty much a singular measurement approach in tension with the diverse measurement approaches used in the late time era. If a different model produced a higher value of the Hubble constant from the CMB, the tension would go away and it might fix other tensions in the cosmology fits too. And, this is far from the only tension that LambdaCDM has with observational evidence, so something about that model needs to be fixed in any case.

LambdaCDM may be a good first order approximation of our universe's cosmology with a small number of parameters. But as our data gets better on multiple fronts, it may not be good enough to fit all the data.

Gialamas (2024) on the other hand, argues basically that the late time measurement may be a local effect. This paper argues that the part of the galaxy where we are measuring the late time Hubble constant may just be randomly non-representative of the late time universe as a whole. In other words, everyone is accurately measuring what they see, but they are failing to take into account a basically random sampling error which causes our little corner of the universe to be weird. This random sampling error may be much bigger than one might naively expect, because these random variations are correlated with each other due to their common cosmological origins in the early universe.

Resolving the source of the still unresolved tension isn't easy, and there are a variety of proposals out there to gather new kinds of data to figure out why there is a tension.

 

[Mordred]

Thanks for the additional references. I'm currently studying each separately. A quick glance I noted several of them suggest an evolving Lambda term which has its own implications in gathering data to help identify the cause of the Lambda term. That in and of itself I consider useful as the cosmological constant has been problematic in terms of the standard model. Some of those links you provided may also be helpful in another line of research I've been keeping track of in terms of The Higgs field as the cosmological constant. One of the problems I noted and have never resolved is that any papers involved typically use the same equations of state terms for the scalar field as has been used for chaotic inflation via the inflaton. That alone I found questionable to say the least as it seems to involve too great an assumption. Which is another line of active research I have been focused on for several years so it will useful to look at the comparisons. Particularly since one of the other issues I found I was struggling with in the Higgs case is how can that lead to a constant density evolution term suggested by the w=-1 relation.

Obviously at this point I'm not forming any opinions of which possibilities is best but rather choose to study each possibility equally. So once again those references you provided I will find useful for various related reasons that in some cases go beyond just the Hubble tension itself. So once again my thanks

 

[Jaime Rudas]

Regarding the Hubble tension, at the Lemaître Conference 2024 taking place at the Vatican Observatory, contributions from Wendy Freedman and Adam Riess were presented today. Slides from Freedman's presentation can be viewed here.

 

[Jaime Rudas]

Slides from Freedman's presentation can be viewed here.

It should be noted that Freedman's results have not yet been published.

 

[Mordred]

Some interesting details in what's shown above. I look forward to the paper itself. There is a particular metalicity relation in the above that definitely peaked my interest. Will have to see what details I can pull on that lol.

I'm glad to see that Freedman suggested that no new physics is required due to JWST measurements.
Thanks for the additional detail.

 

[ohwilleke]

Regarding the Hubble tension, at the Lemaître Conference 2024 taking place at the Vatican Observatory, contributions from Wendy Freedman and Adam Riess were presented today. Slides from Freedman's presentation can be viewed here.

The bottom line from Freedman's presentation is that:

And basically, the presentation convincingly shows that this late time calculation of the Hubble constant measurement is solid and should have a small uncertainty.

The cosmic microwave background measurement mostly from Planck data, in contrast, according to this published paper from 2019 is:

Recent estimates of the Hubble constant from CMB anisotropies by Planck Collaboration, [are] (H0 = 66.93 ± 0.62 km s−1 Mpc−1, Planck Collaboration Int. XLVI 2016)[.]

This is a 1.4 sigma tension before considering Cephid distances (which would be called "consistent with each other), but could rise to as much as 3.4 sigma at the high end of the range after considering them, even though, even at the highest tension it is only a 6% discrepancy in relative terms.

 

[Mordred]

Some further details on the Leavitt Law in regards to Cephied metalicity mentioned above in the Freedman article.
There's a considerable number of papers in regards to calibration using the Milky way and local group. Some examples below

https://ui.adsabs.harvard.edu/abs/2023MNRAS.520.4154M/abstract

https://arxiv.org/abs/2205.06280

The last link above relates this to Hubble constant. In essence forming the first rung of the Cosmological distance ladder.

https://arxiv.org/abs/2103.10894

As this research is related thought I would add to this thread.