Dark energy might not be constant after all

[Filip Larsen]

https://arstechnica.com/science/2024/04/dark-energy-might-not-be-constant-after-all/
https://www.desi.lbl.gov/2024/04/04...recise-measurement-of-the-expanding-universe/

Interesting preliminary indications from DESI (which I did not know about until now).

The Dark Energy Spectroscopic Instrument (DESI)​

The Dark Energy Spectroscopic Instrument (DESI) will measure the effect of dark energy on the expansion of the universe. It will obtain optical spectra for tens of millions of galaxies and quasars, constructing a 3D map spanning the nearby universe to 11 billion light years.

 

[exponent137]

One question:
In https://arxiv.org/pdf/2404.03002.pdf
it is written in the abstract:

"upper limit Sum mν < 0.072 (0.113) eV at 95% confidence for a Sum mν > 0 (Sum mν > 0.059) eV prior."

To which value we can believe more, 0.072 eV, or to 0.113 eV?

 

[Hill]

One question:
In https://arxiv.org/pdf/2404.03002.pdf
it is written in the abstract:

View attachment 342927

"upper limit Sum mν < 0.072 (0.113) eV at 95% confidence for a Sum mν > 0 (Sum mν > 0.059) eV prior."

To which value we can believe more, 0.072 eV, or to 0.113 eV?

As noted in the main text,

 

[exponent137]

So, is 0.113 eV the more correct answer? Let us ignore IH. What is the point of 0.072 eV? To show that the results are more precise?

 

[Bandersnatch]

So, is 0.113 eV the more correct answer? Let us ignore IH. What is the point of 0.072 eV? To show that the results are more precise?

It's not that it's 'more correct'. The result is dependent on what one assumes is the correct lower bound for the sum of neutrino masses. If you assume one thing, it's that. If you assume another, it's the other thing.
They have to assume something, because it's not known. But there are good reasons to pick some specific values, for which they show the corresponding results.

The relevant bit is in section 7.1 (second paragraph).

 

[ohwilleke]

One question:
In https://arxiv.org/pdf/2404.03002.pdf
it is written in the abstract:

View attachment 342927

"upper limit Sum mν < 0.072 (0.113) eV at 95% confidence for a Sum mν > 0 (Sum mν > 0.059) eV prior."

To which value we can believe more, 0.072 eV, or to 0.113 eV?

The second. The merely non-zero Bayesian prior for the sum of the three neutrino masses is contrary to the whole point of using Bayesian statistics (which is to incorporate information that you already know in a prior), and should just be ignored as meaningless.

 

[exponent137]

It's not that it's 'more correct'. The result is dependent on what one assumes is the correct lower bound for the sum of neutrino masses. If you assume one thing, it's that. If you assume another, it's the other thing.
They have to assume something, because it's not known. But there are good reasons to pick some specific values, for which they show the corresponding results.

The relevant bit is in section 7.1 (second paragraph).

I read. One option is for the degenerate case. I suppose that this option is contrary to the measured mass differences of neutrinos? If it is in contradiction with measurements, why it is used? Maybe because it gives some simplified information?