My paper with Leonardo Comini and Avi Loeb, where we revisit the “JWST tension” in models beyond ΛCDM and with spectroscopic data (see this earlier news item), has now officially been published in JHEAp! The full bibliographic coordinates for the paper are JHEAp 53 (2026) 100626. Here is the link to the paper (which is published Open Access).
Beyond ΛCDM with JWST paper accepted in JHEAp!
My paper with Leonardo Comini and Avi Loeb, where we revisit the “JWST tension” in models beyond ΛCDM and with spectroscopic data (see this earlier news item), has been accepted for publication without changes in JHEAp! You can read the preprint version of our paper on arXiv: 2604.13866.
Beyond ΛCDM with JWST
I’m very happy to see my latest paper with my former MSc student Leonardo Comini and Avi Loeb out on arXiv - congratulations to Leonardo who did a significant part of the work, in what is basically the result of his MSc thesis! This work is basically an extension of Mike Boylan-Kolchin’s 2023 paper arguing that early JWST photometric data put significant pressure on the ΛCDM model. We basically asked the question of how this result changed if: 1) a proper Bayesian analysis was carried out, 2) considering also models beyond ΛCDM (e.g. models with a free equation of state or spatial curvature), and 3) using also spectroscopic data which is more reliable? The answer is that carrying out this analysis photometric data actually no longer requires an unusually high star formation efficiency, unlike (surprisingly) spectroscopic data, with the results not changing significantly in models beyond ΛCDM: the conclusion is that the origin of the “JWST tension” is likely astrophysical rather than cosmological. You can read the results in the preprint we just posted on arXiv: 2604.13866.
Multi-field early dark energy
I’m extremely excited to see my latest paper with my outstanding MSc student Marco Bella, Vivian Poulin, and Lloyd Knox out on arXiv - congratulations to Marco who did basically all the work, in what is essentially the result of his MSc thesis! The canonical 1-field axion early dark energy (EDE) model which Vivian and collaborators developed a few years ago faces extremely tight constraints when confronted against Planck PR4 CMB data. In this work we asked ourselves: what happens if we introduce more than 1 axion, a scenario which for instance can be strongly motivated by the string axiverse? The answer is that having 2 axions can significantly help, basically halving the residual Hubble tension even when confronted against Planck PR4 CMB data, whose fit is drastically improved by the fact that the modifications to the expansion history now span a wider redshift range, including the epoch closer to recombination (although, interestingly, having more axions does not seem to improve these results). You can read the results in the preprint we just posted on arXiv: 2604.13535.
BAO and Hubble tension no-go theorem paper published in PRD!
My paper with Davide Pedrotti, Luis Escamilla, Valerio Marra, and Leandros Perivolaropoulos, where we show that the “Hubble tension no-go theorem” forbidding purely post-recombination solutions is robust against a possible miscalibration of BAO measurements, while highlighting the very important role of unanchored SNeIa (see this earlier news item), has now officially been published in PRD, where it has been selected as an Editors’ Suggestion (see this earlier news item)! The full bibliographic coordinates for the paper are Phys. Rev. D 113 (2026) 043507. Here is the link to the paper (which is published Open Access).
BAO and Hubble tension no-go theorem paper selected as Editors' Suggestion in PRD!
My paper with Davide Pedrotti, Luis Escamilla, Valerio Marra, and Leandros Perivolaropoulos, on the implications of a possible BAO miscalibration for the Hubble tension (see this earlier news item), recently accepted for publication in PRD, has also been selected as an Editors’ Suggestion! These make up a small fraction of outstanding papers judged by PRD’s Editors as being particularly important, interesting, and well written, and are highlighted on the journals’ homepage. Great news for a paper which I do not hesitate to place among the top 3 most important papers I ever wrote!
BAO and Hubble tension no-go theorem paper accepted in PRD!
My paper with Davide Pedrotti, Luis Escamilla, Valerio Marra, and Leandros Perivolaropoulos, where we show that the “Hubble tension no-go theorem” forbidding purely post-recombination solutions is robust against a possible miscalibration of BAO measurements, while highlighting the very important role of unanchored SNeIa (see this earlier news item), has been accepted for publication in PRD! Compared to the earlier version there were very minor changes to Fig. 5 and Fig. 10. You can read the preprint version of our paper on arXiv: 2510.01974.
Miguel Sabogal joins my group!
I’m super excited to welcome my new PhD student Miguel Sabogal to my group! Miguel, who is originally from Colombia, previously did his MSc in Brazil at the Federal University of Rio Grande do Sul under the supervision of my friend and colleague Rafael Nunes, working broadly on tests of fundamental physics from cosmological data: with me, he will keep going in this direction, with an eye in particular to cosmological tensions. Miguel already has an outstanding publication record, with several high-impact, original, and extremely interesting publications, including a PRL. Many of my colleagues I’ve spoken to think of Miguel as the potential future of cosmology in Latin America, and I am excited that he chose to join my group. Welcome Miguel!
BAO and Hubble tension no-go theorem
I’m extremely excited to finally see my latest paper with Davide Pedrotti, Luis Escamilla, Valerio Marra, and Leandros Perivolaropoulos, finally out on the arXiv - kudos to Davide who did all the heavy-lifting in what I do not hesitate to place among the three most important papers I ever wrote! This paper is about what we could call the “Hubble tension no-go theorem”, which forbids purely post-recombination solutions due to the constraints BAO impose on the product of the sound horizon and the Hubble constant. However, the pipeline from which BAO measurements are obtained requires assuming a fiducial cosmological model, with the choice falling on ΛCDM: many have therefore wondered whether we can trust these measurements when testing late-time modifications to ΛCDM, and this is the most frequently invoked loophole to the no-go theorem. In this work we have played devil’s advocate and showed that, even if BAO measurements were to be grossly (and unrealistically) biased by fiducial cosmology assumptions, this would still not be sufficient to rescue post-recombination solutions to the Hubble tension, primarily because of the extremely tight constraints on the (unnormalized) shape of the expansion history from unanchored SNeIa, whose role in the Hubble tension so far has been underappreciated. You can read our results in the preprint we just posted on arXiv: 2510.01974.
Visit by Enrico Specogna
For the next two days we have Enrico Specogna visiting us from the University of Sheffield! Enrico is currently a PhD student working with Eleonora Di Valentino on several topics of interest to our group, such as cosmological tensions, massive neutrinos, inflation, and modified gravity. He will be delivering a talk by the title of “Modified gravity & friends vs current CMB data”. Welcome Enrico!
CosmoVerse white paper published in PDU!
The CosmoVerse white paper, produced within the CosmoVerse COST Action and discussing in detail the state-of-the-art regarding a number of observational tensions in cosmology (see this earlier news item), has now officially been published in PDU! The full bibliographic coordinates for the paper are Phys. Dark Univ. 49 (2025) 101965. Here is the link to the paper (which is published Open Access).
Zakaria Belkhadria wins STSM grant to visit Trento
Congratulations to Zakaria Belkhadria, who recently received his PhD from the University of Cagliari and the University of Geneva, and who was awarded a COST short-term scientific mission (STSM) grant within the CosmoVerse COST Action, which will fund his short visit to the University of Trento in October! Zakaria will be working with Max Rinaldi and myself on strong-field tests of modified gravity models which show promise in the Hubble tension context.
CosmoVerse white paper accepted in PDU!
It is a great pleasure to see the CosmoVerse white paper, produced within the CosmoVerse COST Action and discussing in detail the state-of-the-art regarding a number of observational tensions in cosmology (see this earlier news item), accepted for publication in PDU! I am doubly pleased both as author and Editor of PDU, as this paper will significantly increase the journal’s visibility. You can read the preprint version of the paper on arXiv: 2504.01669.
CosmoVerse white paper
Very happy to see the CosmoVerse white paper, produced within the CosmoVerse COST Action, out today! The white paper discusses in detail the state-of-the-art regarding a number of observational tensions in cosmology (among all the Hubble tension) and how these may be solved either through new fundamental physics or systematics. Huge congrats are due to my friends and colleagues Eleonora Di Valentino and Jackson Levi Said for leading this massive effort featuring over 400 pages and over 500 authors, which required significant coordination and management skills. I myself was one of the Section Coordinators, for section 4.1.3 on extra relativistic degrees of freedom. You can read our results in the preprint we just posted on arXiv: 2504.01669.
Visit by Lei Zu
Today we have the pleasure of hosting Lei Zu (祖磊), currently a postdoc at the National Centre for Nuclear Research (NCBJ) in Warsaw, and an expert on various signatures of dark sector physics in astrophysical and cosmological observables. Lei delivered a very nice seminar by the title of “Exploring dark matter non-gravitational interactions through weak lensing”. Welcome Lei!
Non-parametric expansion history reconstruction paper published in PRD!
My paper with Jun-Qian Jiang, Davide Pedrotti, and Simony Santos da Costa, where we perform a non-parametric reconstruction of the late-time expansion history in light of DESI BAO data (see this earlier news item), has now officially been published in PRD! The full bibliographic coordinates for the paper are Phys. Rev. D 110 (2024) 123519. Here is the link to the paper.
Non-parametric expansion history reconstruction paper accepted in PRD!
My paper with Jun-Qian Jiang, Davide Pedrotti, and Simony Santos da Costa (first one entirely produced within my group), where we perform a non-parametric reconstruction of the late-time expansion history in light of DESI BAO data (see this earlier news item), has been accepted for publication in PRD! Compared to the earlier version, there have been minor changes to the plots and title, but our main results are unaltered. You can read the preprint version of the paper on arXiv: 2408.02365.
Varying electron mass and ΛsCDM paper published in PDU!
My paper with Yo Toda, William Giarè, Emre Özülker, and Eleonora Di Valentino, where we attempt to solve the Hubble tension combining a spatially uniform time-varying electron mass in a non-spatially flat Universe, and the ΛsCDM model, featuring a late-time sign-switching cosmological constant (see this earlier news item), has now officially been published in PDU! The full bibliographic coordinates for the paper are Phys. Dark Univ. 46 (2024) 101676. Here is the link to the paper (which is published Open Access).
Varying electron mass and ΛsCDM paper accepted in PDU!
My paper with Yo Toda, William Giarè, Emre Özülker, and Eleonora Di Valentino, where we attempt to solve the Hubble tension combining a spatially uniform time-varying electron mass in a non-spatially flat Universe, and the ΛsCDM model, featuring a late-time sign-switching cosmological constant (see this earlier news item), has been accepted for publication in PDU! Minor revisions compared to the previous version include a small change to the title, small updates to the figures and tables for consistency, and especially a proper Bayesian evidence-based model comparison analysis. You can read the preprint version of the paper on arXiv: 2407.01173.
Hubble tension, Ωm, and ωc
A very busy week, with another paper produced almost entirely within my group, just in time for wrapping up for holidays! With Davide Pedrotti, Jun-Qian Jiang, Luis Escamilla, and Simony Santos da Costa, we argue that the Hubble tension is inherently multidimensional, and that the matter density parameter Ωm and cold dark matter physical density ωc play key roles. In particular, we analytically explained why any model aiming to solve the Hubble tension will inevitably lead to an increase in ωc (because both Ωm and ωb are precisely calibrated by BAO and/or SNeIa, and BBN respectively) and, by extension, S8 (with potential problems for the S8 discrepancy), and explicitly verified that this holds on real data. We then argued that if cosmologists interested in solving the Hubble tension could ask for just one present from Father Christmas…well, then they really should wish to know the value of Ωm chosen by Nature - or, in practical terms, they should wish for a calibration of Ωm which is as reliable and model-independent as possible, and we put forward some ideas on how to achieve this. You can read our results in the preprint we just posted on arXiv: 2408.04530.
