Next seminar will be Wed March 5th 9:30am UK time with Elsa Teixeira (LUPM/Université de Montpellier) talking about "Illuminating cosmic tensions with a coupled scalar dark sector”. Register here:

https://t.co/V3gCexpZT6

Hey Trump voters. Hate to break it to you - but here’s what actually happened on Tuesday. Watch. Bernie explained it 20 years ago.

https://t.co/u2502kbXPy

Today is a big day. Good luck America!

A new PhD position on observational cosmology at CIEMAT (Madrid) is opening soon! 🔭 See the poster below for more details, and contact me if you are interested!

Lately, there have been different reports about the Hubble Tension from JWST, with different teams and methods. It’s been hard to follow. But initial sample sizes were small so in a new paper we combined, for the first time, all measurements to date, includes 5 JWST programs,

Congratulations to Spain 🇪🇦 on winning the football olympic gold medal after a great game against France 🇨🇵! Def deserved it. Also, absolutely unrelated, I will stop any collaboration with people from Spain nor visit the country or invite people for the next 4 years.

Fun day at the olympics in Marseille! Allez les bleus! 🥳🇫🇷

with awesome collaborators Tristan Smith, Rodrigo Calderon and Theo Simon. More details here:

Of course EDE, varying me are not well motivated models beyond those tensions, and we need to work on alternative realizations of these ideas with theory input. But these phenomenological considerations are important in that regard. See also the "step Neff" and PMF in appendix.

what's more: they are consequences for S8, the age of the universe, the baryon density. Under LCDM, the "SH0ES universe" has a large S8 and a small tU. In fact early time new physics *decreases* S8, but not tU that is a robust prediction of the SH0ES calibrated SN1a/BAO.

So the ``cosmic calibration tension'' points either to a targeted modification of the pre-recombination expansion history (Neff, EDE etc), or to a broader change, affecting recombination and the late-time dynamics (e.g. varying me+curvature).

But there's a twist! the problem above is the strong constraints to Om_m from BAO/SN1a. Opening the late-universe dynamics can relax these constraints: varying me+curvature does *great*. This does not help EDE however.

This is why a model like Neff, or EDE (shown here in orange) that compensates the effect of om_m does better than a model playing with recombination (like varying electron mass me, also shown in green). Neff and EDE have the right correlation with h and om_m, varying me doesnt.

In terms of cosmo parameters, we could have equally talked about "the physical matter density tension". Such large matter density is of course excluded by the CMB. This means any new physics must be able to accommodate these effects or they will be excluded.

*Uncalibrated* BAO and SN1a constrain (under LCDM) Omega_m, H0*rd and the product H0*Lb^2, with Lb the SN1a magnitude. The SH0ES magnitude (in blue) implies a larger H0 than Planck/rs (in red). But not only! See the increase in om_m since om_m = Om_m*h^2. They go hand in hand.

The core problem (which is known but often overlooked) is the calibration of the distance diagrams built either with SN1a or BAO. When Planck/LCDM sound horizon (red) and SH0ES magnitude (blue) is used, they disagree strongly (top). One needs to reduce the sound horizon (bottom)

3 years ago, we wrote the H0 olympics, where models were ranked for their ability to alleviate the ``H0 tension''. Yet, it was not always clear why some models did better than others. Today's paper clarify this and explains why I think we should stop calling it "the H0 tension".

Despite the rain, this was an AMAZING show ! Vive la France! And good luck to all the athletes and country involved in #Paris2024 let's unite and have fun!