My paper with Jun-Qian Jiang, William Giarè, Stefano Gariazzo, Maria Giovanna Dainotti, Eleonora Di Valentino, Olga Mena, Davide Pedrotti, and Simony Santos da Costa, where we investigate the status of (positive) neutrino mass cosmology after the latest DESI measurements (see this earlier news item), has been accepted for publication in JCAP! The paper has undergone has a substantial revision, which resulted in the addition of several appendices clarifying various technical aspects of the analysis (e.g. cosmology-internal tension, impact of PR4 likelihoods, and H0 versus MB prior among others), as well as an additional useful plot, and useful discussions on the neutrino mass ordering: however, the main results are unaltered, and are now more robust. You can read the preprint version of the paper on arXiv: 2407.18047.
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.
Alessandro La Sala joins my group!
Today Alessandro La Sala officially joins my group, thus becoming the first BSc student to write his BSc thesis/final project under my supervision. Alessandro is enrolled in the Mathematics BSc, but has a keen interest in physics, and his project will be on the topic of General Relativity and Dark Energy. Welcome Alessandro!
Solar chameleons paper published in PRD!
My paper with Tom O'Shea, Anne Davis, Maurizio Giannotti, Luca Visinelli, and Julia Vogel, where we revisited the issue of production of Solar chameleons (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) 063027. Here is the link to the paper (which is published Open Access).
Stochastic gravitational wave background from cosmologically coupled black holes
Very happy to see my latest paper with Marco Calzà, Francesco Gianesello, and Max Rinaldi out! This is a 100% “made in Trentino” paper, and more precisely made within the Theoretical Gravitation and Cosmology Group led by myself and Max. At some point in 2023, the possibility that dark energy could be sourced by cosmologically coupled black holes (BHs), whose mass increases in time through purely cosmological growth even in the absence of accretion and merger events, received a lot of interest, especially given the possibility that signatures of such a coupling could have been observed in the growth of supermassive BHs in red-sequence elliptical galaxies. In today’s paper we show that mergers of such cosmologically coupled BHs would lead to a stochastic gravitational wave background whose strength is significantly larger (up to an order of magnitude stronger!) than the standard one from mergers of uncoupled BHs, with very interesting implications for the signal observed last year by pulsar timing arrays (among which NANOGrav, EPTA, PPTA, and CPTA), which is a bit too strong to be easily explainable by mergers of standard BHs. You can read our results in the preprint we just posted on arXiv: 2409.01801.
Solar chameleons paper accepted in PRD!
My paper with Tom O'Shea, Anne Davis, Maurizio Giannotti, Luca Visinelli, and Julia Vogel, where we revisited the issue of production of Solar chameleons (see this earlier news item), has been accepted for publication in PRD! Minor revisions compared to the previous version include a rough estimate of how much the CAST bound on the chameleon-photon coupling changes accounting for the production channels we studied. You can read the preprint version of the paper on arXiv: 2406.01691.
Non-parametric expansion history reconstruction and Hubble tension after DESI
I’m particularly excited and proud about today’s paper, which is the first one written entirely and exclusively with members of my group: visiting PhD student Jun-Qian Jiang (who did all the heavy lifting), PhD student Davide Pedrotti, and postdoc Simony Santos da Costa. What we did has been to perform a non-parametric reconstruction of the late-time expansion history in light of DESI BAO data, combined with various SNeIa datasets, using both interpolation and Gaussian Process reconstruction techniques, and studying implications for the Hubble tension. We find that the shape of the expansion history cannot deviate more than 10% from that of ΛCDM, but within that 10% we find interesting deviations which could hint to a non-monotonic/oscillatory behaviour of the expansion rate (and therefore of the dark energy component). I really believe that this can be a pretty important paper, as it represents a much needed revisitation in light of DESI of two seminal papers in the expansion history reconstrcution and Hubble tension literature: the famous “Trouble with H0” paper by Bernal, Verde, & Riess, and the equally famous “Sounds discordant” paper by Aylor and collaborators. You can read our results in the preprint we just posted on arXiv: 2408.02365.
Negative cosmological constant and JWST paper (part 2) published in JCAP!
My paper with Nicola Menci, Shahnawaz Adil, Upala Mukhopadhyay, and Anjan Sen, where we robustly compare a dark energy model featuring a negative cosmological constant against JWST data (see this earlier news item), has now officially been published in JCAP! The full bibliographic coordinates for the paper are JCAP 2407 (2024) 072. Here is the link to the paper (which is published Open Access).
Post-DESI neutrino cosmology
Another paper out today! Led by Jun-Qian Jiang and William Giarè (both of whom did a huge amount of work), and together with Stefano Gariazzo, Maria Giovanna Dainotti, Eleonora Di Valentino, Olga Mena, Davide Pedrotti, and Simony Santos da Costa, we investigate the status of (positive) neutrino mass cosmology after the latest DESI measurements. We find very tight upper limits on the sum of the neutrino masses, a strong preference for the normal ordering, and a significant tension with terrestrial observations, all of which we carefully quantify. We also studied the impact of allowing the dark energy component to be non-phantom, which makes all the previous conclusions somewhat stronger, and highlights an interesting synergy between laboratory experiments aimed at determining the neutrino mass ordering, and the nature of dark energy. You can read our results in the preprint we just posted on arXiv: 2407.18047.
Negative cosmological constant and JWST paper (part 2) accepted in JCAP!
My paper with with with Nicola Menci, Shahnawaz Adil, Upala Mukhopadhyay, and Anjan Sen, where we robustly compare a dark energy model featuring a negative cosmological constant against JWST data (see this earlier news item), has been accepted for publication in JCAP! The results are basically unchanged compared to our earlier version, with certain aspects of our analysis better clarified. You can read the preprint version of the paper on arXiv: 2401.12659.
Attempting to solve the Hubble tension combining varying electron mass and ΛsCDM
I’m very, very glad to see my latest work with Yo Toda, William Giarè, Emre Özülker, and Eleonora Di Valentino finally out on arXiv after several months of hard work (especially by the first author Yo who did all the heavy lifting)! The idea is motivated by my seven hints paper (see this earlier news item) arguing that solving the Hubble tension may require a combination of pre- and post-recombination new physics, and here we attempted to construct precisely such a combination, focusing on models which individually worked well in the pre- and post-recombination era so far: 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 (from negative to positive). In the end the idea didn’t quite work, but we still decided to document our attempt because we learned a great deal about potential difficulties and drew what we hope are important general lessons for future endeavours: for the record, these are reported between Pages 10 and 13 and, spoiler, Ωm plays a crucial role in explaining why this didn’t work. A fun fact Özgür Akarsu reminded me of is that around minute 44 of my Universe Today Podcast interview with Fraser Cain back in November (see this earlier news item) I actually gave a very detailed spoiler of this project, as I had spoken to Yo a few days back so we had just gotten it started (and I had quite high hopes on this working out, which it certainly did in the sense of learning a whole lot of new things, although not in the way I initially expected). You can read our results in the preprint we just posted on arXiv: 2407.01173.
Solar chameleons revisited: 2024 edition
I’m extremely happy to see our latest work led by the brilliant Tomás (Tom) O'Shea, together with Anne Davis, my fellow countryman (we are both from Terracina) Maurizio Giannotti, Luca Visinelli, and Julia Vogel, out on arXiv! This was a technical tour-de-force led by Tom where we revisited the issue of production of chameleons (which could be relevant to the dark energy problem) in the Sun, whose state-of-the-art dated back to 2012, and partially motivated by the earlier work of myself, Luca, and Anne. The resulting spectrum includes a number of previously overlooked contributions which turn out to make an important difference, and our results can be extremely relevant for future experiments such as IAXO. While in our work we only included the contribution from transverse photons, the study of longitudinal plasmons is certainly relevant and in progress. You can read our results in the preprint we just posted on arXiv: 2406.01691.
Visit to Camerino
Today and for the next two days I am visiting the University of Camerino, where I will be giving a talk on “Searching for dark energy off the beaten track” (see poster below, slides here). I will be hosted by Orlando Luongo, whom I look forward to meeting in person after reading his works for many years. I look forward to a nice visit in a charming city!
State of the dark energy equation of state paper published in JCAP!
My paper on the dark energy equation of state with Luis Escamilla, William Giarè, Eleonora Di Valentino, and Rafael Nunes, which I previously reported on in an earlier news item, has now officially been published in JCAP! The full bibliographic coordinates for the paper are JCAP 2405 (2024) 091. Here is the link to the paper (which is published Open Access).
State of the dark energy equation of state paper accepted in JCAP!
My paper with with Luis Escamilla, William Giarè, Eleonora Di Valentino, and Rafael Nunes, where we present state-of-the-art constraints on the dark energy equation of state from a number of cosmological probes (see this earlier news item), has been accepted for publication in JCAP! There were a few changes, mostly making a few parts of the discussion clearer, but the results are otherwise completely unchanged compared to the previous version we posted this summer. You can read the preprint version of the paper on arXiv: 2307.14802.
Admissions for PhD in Physics in Trento!
The University of Trento welcomes applications for admission to the 40th cycle of the PhD in Physics, for positions starting on November 1, 2024 (see here for Italian link, here for English link, and here for much more detailed information): this year we have a total of 19 positions, 14 of which with scholarship, and 4 of which are “open positions”, i.e. not tied to any specific topic. Applicants interested in working within the Theoretical Gravitation and Cosmology group (basically either with me or Prof. Rinaldi) would be competing for these 4 “open positions” - however, another possible channel for working with us is to apply for one of the 3 INFN funded-positions (Section “D, E - Particle, astroparticle, nuclear, theoretical physics, related technologies and applications, including medical Physics”), which are de facto “open positions” (as long as the topic one ends up working on is related to INFN research themes, for instance the group’s current PhD students Chiara Cecchini and Davide Pedrotti were awarded one of these positions). I cannot stress enough that competition for these positions is extremely strong, with an oversubscription ratio much higher than for the other (reserved) positions: a corollary is that there is no guarantee our group will be taking new PhD students, given that it really depends on the personal interests of those who will be awarded these positions (however, I can anticipate that I will be taking a most one new PhD student - for a rough guideline on possible topics one could work on with me, please see this link, section “First call 40°cycle - Other research topics”, subsection “FT - Theoretical and computational physics”, and refer to the topic “Dark matter and dark energy in the era of precision multi-messenger cosmology and cosmic tensions (Vagnozzi)”). If you are interested in working with us, please make this very clear in your “lettera motivazionale” (“statement of purpose”), which plays an extremely important role in the evaluation of candidates, so please take it very seriously. The application deadline is May 15, 2024 at 16:00 Italy time, but applicants are strongly encouraged to apply well in advance of the deadline - if you are interested in working within our group, please do not hesitate to reach out either to me or Prof. Rinaldi (or both) and apply as soon as possible!
Mattia Scotto joins my group!
My group keeps expanding, and now includes Mattia Scotto as well! He will be working on his Master’s thesis under my supervision, where we plan on studying various cosmological signatures of dark energy models featuring a negative cosmological constant (perfect timing given today’s new preprint!), and how the signatures we will find can help us distinguish these models from the cosmological constant of ΛCDM. Welcome Mattia, and I’m looking forward to our work together!
Negative cosmological constant and JWST (part 2)
Together with Nicola Menci, Shahnawaz Adil, Upala Mukhopadhyay, and Anjan Sen, today we posted a new preprint which is basically the sequel to our earlier negative cosmological constant and JWST paper published in JCAP. What we did here, in no small part thanks to Nicola’s contribution, was to perform a more thorough analysis of JWST data, which significantly strengthens our earlier conclusions and shows that a dark energy model featuring a negative cosmological constant is a very interesting candidate model in light of the JWST observations. One notable addition was our study not only of photometric observations, but also spectroscopic observations from the FRESCO survey, which again confirm the earlier results and at the same time make them much more robust. It was great fun working on this paper, and I learned a lot about high-redshift galaxies! You can read our results in the preprint we just posted on arXiv: 2401.12659.
Official openings for 2 DARKTRACK-funded postdoc positions
I am officially hiring! Applications are now welcome for 2 DARKTRACK-funded postdoc positions, for which I was previously gathering expressions of interest. Two positions are available, depending on whether or not the candidate holds a PhD at the time of the application:
* call 185/2023: lavoraconnoi.unitn.it/en/research-contracts/department-physics-call-selections-awarding-no-1-research-fellowship-decree-no-185-2023 (for candidates already holding a PhD)
* call 186/2023: lavoraconnoi.unitn.it/en/research-contracts/department-physics-call-selections-awarding-no-1-research-fellowship-decree-no-186-2023 (for candidates yet to obtain their PhD)
Please have a look at the INSPIRE job ad for further details, but make sure you submit all your application material to the above links, as we cannot consider material received via other channels. Please reach out to me if you have further questions about the project or the positions!