Quanta: Gaia data increases the Hubble tension!

[notFritzArgelander]

https://www.quantamagazine.org/astronom ... d21d14a9ea

[ThinkerX]

reality apparently contradicting itself?

[notFritzArgelander]

reality apparently contradicting itself?

Not really. The high value is from recent times and the low value is from the CMB so rather older.

[pakarinen]

Oh boy! Mayhem!

[pakarinen]

https://iopscience.iop.org/article/10.3 ... 213/abdbaf

[notFritzArgelander]

Great fun!

[notFritzArgelander]

https://iopscience.iop.org/article/10.3 ... 213/abdbaf

I want to thank you again after many months for posting this link to the paper. Unlike the findings in another recent thread that the length scale for homogeneity and isotropy is a factor of 3 larger than thought, the measurement discrepancy between ancient and more recent measures of the Hubble parameter gives a very clean and compelling case that there is something afoot here.

I've read the paper you graciously posted several times over the last few months. Each time my consideration that errors in the SN Ia method fades a little. We're not at the 5 sigma level of significance yet, but I am becoming quite certain that ΛCDM, the standard cosmology, will have to be changed.

Most likely change? Λ can't be modeled as a cosmological constant but is some kind of field having an equation of state that varies with time or temperature. There will have to be some sort of negative pressure fluid in the source term of the Friedmann equations.

[ThinkerX]

https://iopscience.iop.org/article/10.3 ... 213/abdbaf

I want to thank you again after many months for posting this link to the paper. Unlike the findings in another recent thread that the length scale for homogeneity and isotropy is a factor of 3 larger than thought, the measurement discrepancy between ancient and more recent measures of the Hubble parameter gives a very clean and compelling case that there is something afoot here.

I've read the paper you graciously posted several times over the last few months. Each time my consideration that errors in the SN Ia method fades a little. We're not at the 5 sigma level of significance yet, but I am becoming quite certain that ΛCDM, the standard cosmology, will have to be changed.

Most likely change? Λ can't be modeled as a cosmological constant but is some kind of field having an equation of state that varies with time or temperature. There will have to be some sort of negative pressure fluid in the source term of the Friedmann equations.

seeking clarity here Fritz,

It sounds almost like you are putting greater credence into the photometric (SN Ia) distances than other distance methods.

as to the 'negative pressure fluid' - would that be 'dark energy?'

[notFritzArgelander]

https://iopscience.iop.org/article/10.3 ... 213/abdbaf

I want to thank you again after many months for posting this link to the paper. Unlike the findings in another recent thread that the length scale for homogeneity and isotropy is a factor of 3 larger than thought, the measurement discrepancy between ancient and more recent measures of the Hubble parameter gives a very clean and compelling case that there is something afoot here.

I've read the paper you graciously posted several times over the last few months. Each time my consideration that errors in the SN Ia method fades a little. We're not at the 5 sigma level of significance yet, but I am becoming quite certain that ΛCDM, the standard cosmology, will have to be changed.

Most likely change? Λ can't be modeled as a cosmological constant but is some kind of field having an equation of state that varies with time or temperature. There will have to be some sort of negative pressure fluid in the source term of the Friedmann equations.

seeking clarity here Fritz,

It sounds almost like you are putting greater credence into the photometric (SN Ia) distances than other distance methods.

No, not at all. My hierarchy of preferred distance methods is, was, and always shall be trigonometric parallaxes first. The paper that pakarinen posted uses Gaia trigonometric parallaxes to put more solid foundations under the Cepheid period-luminosity relationship and THOSE photometric results in turn provide a better foundation for the SN Ia photometric distances. The weakest link has always been the Cepheid trigonometric parallaxes and Gaia has strengthened that link considerably.

The catalog of Cepheids in SN Ia host galaxies is expected to increase by roughly 40 so we are looking (all other things remaining roughly the same) at a significance of more than 6 sigma. At that point a "cosmological constant model" of dark energy is discovered to be falsified.

]as to the 'negative pressure fluid' - would that be 'dark energy?'

Well yes but dark energy isn't one thing. There are more theories about dark energy than there are theorists, likely.

Broadly speaking the possibilities for dark energy include:

1) the cosmological constant, the intrinsic energy of having space time (this is the only flavor of dark energy that is imperiled
there are several flavors of cosmological constant as well. https://en.wikipedia.org/wiki/Dark_ener ... l_constant

2) dark energy could be a dynamical field, these are quintessence models https://en.wikipedia.org/wiki/Dark_energy#Quintessence however i caution that i cannot reconcile quintessence models with variable (in space and time) fundamental constants or inhomogeneities. Emmy Noether is "she who must be obeyed" and fanciful theorists need reminding of that. i draw attention to a subspecies of quintessence dark energy, the quintom scenario. https://en.wikipedia.org/wiki/Quintom_scenario

3) variable dark energy models appear to be what the Hubble tension naively implies https://en.wikipedia.org/wiki/Quintom_scenario

4) lastly there are attempts to solve dark energy and dark matter with a single proposal https://en.wikipedia.org/wiki/Dark_ener ... ark_energy

i have a fondness for two for one solutions so i'll quote that section.

This class of theories attempts to come up with an all-encompassing theory of both dark matter and dark energy as a single phenomenon that modifies the laws of gravity at various scales. This could, for example, treat dark energy and dark matter as different facets of the same unknown substance,[55] or postulate that cold dark matter decays into dark energy.[56] Another class of theories that unifies dark matter and dark energy are suggested to be covariant theories of modified gravities. These theories alter the dynamics of the spacetime such that the modified dynamics stems to what have been assigned to the presence of dark energy and dark matter.[57] Dark energy could in principle interact not only with the rest of the dark sector, but also with ordinary matter. However, cosmology alone is not sufficient to effectively constrain the strength of the coupling between dark energy and baryons, so that other indirect techniques or laboratory searches have to be adopted.[58]