At a recent DESY (Hamburg) colloquium, I gave a review talk on “Resolving the Hubble Tension with New Early Dark Energy.”
I explained how the DESI anomaly might be connected to the Hubble tension and have an early-universe explanation in terms of dark acoustic oscillations.
This builds on earlier work on New Early Dark Energy, with excellent collaborators: Florian Niedermann, Mathias Garny, Henrique Rubira, Aleksandr Chatrchyan, Juan Cruz, Emil Brinch Holm, Vivian Poulin, Thomas Tram, Steen Hannestad …
A new early-universe explanation of the DESI anomaly connecting to the predictions of our solution to the Hubble tension in collaboration with Mathias Garny and Florian Niedermann: https://arxiv.org/abs/2512.15870
The presence of a Dark Acoustic Oscillation (DAO) near the actual BAO may appear as a single BAO-only feature with a slightly shifted peak position, which could bias the DESI BAO measurements, thereby explaining the anomaly in the DESI DR2 data without invoking late-time-evolving Dark Energy. The DAO predicted in our model for solving the Hubble tension, Hot New Early Dark Energy (Hot NEDE) with Dark Radiation Matter Decoupling (DRMD), also meets the requirements for explaining the DESI results, as shown in the leftmost panel of the figure below. The green curve is the favoured DAO position by the DESI DR2 data on small scales, and the dotted black line is the prediction of DRMD in Hot NEDE, when solving the Hubble tension.
New community report today uses different methods and techniques to establish the value of the Hubble constant to 1% precision, H0=73.50+/-0.81 km/s/Mpc, confirming the Hubble tension at more than 5-sigma.
This means that our current standard model of the Universe, the ΛCDM model, can not describe the real Universe as we observe it, and we must move to finding the correct model of our Universe replacing ΛCDM.
New Early Dark Energy (NEDE) has proven itself to be a promising framework in which to search for the solution to the Hubble tension (see previous posts), and we will keep intensifying our efforts to explore NEDE.
To make sense of the Hubble tension, it is essential to have a simple (in terms of ideas), convincing solution. In a new paper, we present a new microscopic Hot NEDE model of the dark sector based on well-known fundamental principles, gauge symmetry, and spontaneous symmetry breaking, which resolves the Hubble tension. We also discuss how this solution can be further tested with future precision data.
Profile likelihood curves for the model from our paper can be seen below.
Work in collaboration with Mathias Garny, Florian Niedermann and Henrique Rubira.
“Simplicity is part of what I mean by beauty, but it is a simplicity of ideas, not simplicity of a mechanical sort that can be measured by counting equations or symbols.”
In a new paper, “I demonstrate that soft graviton modes in de Sitter are the Goldstone modes of the spontaneously broken asymptotic symmetry group of de Sitter. I then show that any local measurement, including the effects of the environment, will collapse the symmetric state onto the broken state in the large volume limit. In any discussion involving observers, de Sitter is, therefore, best described globally by the broken phase, while local observers, in the small volume limit, can not discriminate between different degenerate global vacuum states, and are therefore best described by the symmetric state. This illuminates the physical nature of soft graviton modes in de Sitter.”
As a bonus, I also speculate about the possibility that a new type of crystals, with the same symmetry-breaking pattern as discussed in the paper, could be realized in the laboratory as an analog system of de Sitter and eternal inflation.
In a new paper “we explore the possibility that exotic forms of dark matter could expose humans on Earth or on prolonged space travel to a significant radiation dose. The radiation exposure from dark matter interacting with nuclei in the human body is generally assumed to be negligible compared to other sources of background radiation. However, as we discuss here, current data allow for dark matter models where this is not necessarily true”. See: https://arxiv.org/abs/2411.10521
New distance-ladder independent measurement using type II SN finds H0 = 74.9 \pm 1.9 (stat) km/s/Mpc in consistency with SH0ES and further confirming the Hubble tension: https://arxiv.org/abs/2411.04968
In a new paper with Aleksandr Chatrchyan, Florian Niedermann, and Vivian Poulin (https://arxiv.org/abs/2408.14537), we generalize the treatment of the NEDE fluid in the Cold NEDE model and test it against updated CMB and Supernovae data. We show that in the Cold NEDE model, the NEDE fluid can, as previously anticipated, be described as a mix of stiff fluid and radiation consistently with data.
The new CMB Planck NPIPE data and Pantheon+ supernova data slightly increase the tension between ΛCDM and SH0ES. This similarly slightly increases the residual tension in (N)EDE models when relieving the Hubble tension, with Cold NEDE doing slightly better than AxiEDE and other EDE-type models. On the other hand, we know from other studies that the recent DESI data pulls in the opposite direction toward reducing the residual tension by a similar amount. In conclusion, further improvements in data and NEDE model building provide a constructive and promising way forward.
Finally, we have made a non-trivial test of the Cold NEDE model. In the Cold NEDE model, it is a theoretical prediction that the ratio between the Hubble rate at the time of the phase transition, H*, and the mass of the trigger field, m, should satisfy H*/m ~ 0.2. Being agnostic about the underlying model and fitting H* and m as free parameters to the data is a way of testing this specific prediction of Cold NEDE. It is spectacular that we find a peak in the probability distribution for H*/m between 0.20 and 0.22 as predicted (see figure below).
Two new analyses of the Hubble tension are based solely on data from the JWST telescope and serve as a check of the measurements using the Hubble Space Telescope (HST), which initially led to the tension in the first place. In the paper today (https://arxiv.org/abs/2408.11770), a value of H0 of 72.6 plus-minus 2.0 km/s/Mpc using JWST data alone is reported. This is also consistent with previous values reported by SH0ES using HST data and consistent with the slightly lower values reported by the CCHP team in another analysis based on JWST data alone (https://arxiv.org/abs/2408.06153) when accounting for the smaller subsample of supernovae used by CCHP. Restricting their analysis to the same smaller subsample as used by CCHP, the SH0ES team reproduces their values, a strong indication of overall agreement. It seems we are very close to a confirmation of the Hubble tension independent from the original HST data.
