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 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.
Jun-Qian Jiang joins my group!
I’m very happy to welcome my latest group member, Jun-Qian Jiang (江俊钱)! Jun-Qian is currently a PhD student at the University of Chinese Academy of Sciences under the supervision of Prof. Yun-Song Piao, and has been doing a lot of interesting and very diversified work in the fields of cosmological tensions, inflation, gravitational waves, and so on. He joins my group for the next 6 months as a long-term visiting PhD student. We still have to figure out what we will be working on, but it likely will have to do with cosmological tensions and possibly implications for inflation. Welcome Jun-Qian, and I hope you will enjoy your stay in Italy!
Tonale Winter School
This week I’m travelling to Passo del Tonale to lecture at the 2023 Tonale Winter School on Cosmology. The weather is fortunately fantastic, with clear skies and a lot of snow (below is the view from my hotel window)! For those of you who might be interested, below are the slides I will use during the lectures, and the questions which will be discussed in the working group sessions:
Lecture 1: Basics of theoretical and observational cosmology [Slides]
Lecture 2: Measuring the Hubble constant – the Hubble tension [Slides]
Lecture 3: How (not) to solve the Hubble tension? [Slides]
Lecture 4: Other tensions and challenges for ΛCDM [Slides]
I have really fond memories from the time I attended as a student in 2014 (fun fact: my roommate was Vivian Poulin, now one of the big names in the Hubble tension game), and I’m looking forward to an exciting week!
Davide Pedrotti (re)joins my group!
Today Davide Pedrotti, after an excellent MSc defense, (re)joins my group as a PhD student. We will be starting some very cool work on cosmological tensions, while also carrying on Davide’s earlier research interests in black hole physics. Stay tuned in particular for our upcoming paper on the connection between quasinormal modes and shadows for rotating regular BHs, which constituted a major part of Davide’s MSc thesis! Welcome (back) Davide!
Seven hints paper makes cover page of September issue!
My seven hints paper - Universe 9 (2023) 393 - has been selected as cover story for the September 2023 issue (Volume 9, Issue 9) of Universe! The production team did a very nice job in designing the cover story image, which you can find here. My paper was also selected as a Feature Paper and an Editor’s Choice. I also recommend to take a look at the Special Issue where my paper was published, which features a bunch of other really interesting papers!
PhD defense of Tiziano Schiavone
Today I had the pleasure of serving as external committee member for the PhD thesis discussion of Tiziano Schiavone, a PhD student at the University of Pisa supervised by Giovanni Marozzi, Giovanni Montani, and Giuseppe Fanizza. Tiziano wrote an excellent thesis by the title of “Large-scale structure of the Universe in General Relativity and beyond”, which on the one hand studied the impact of local inhomogeneities on cosmological observables, and on the other hand examined ways to distinguish between ΛCDM and competing cosmological models, particularly those based on modifications to gravity, especially in light of cosmological tensions. The other two committee members were my collaborator Eleonora Di Valentino and Scilla Degl’Innocenti. Unfortunately I could not be present in person for the first ever PhD defense of which I am committe member (I would have loved to visit the beautiful city of Pisa after many years). Tiziano’s defense was excellent (the final mark we gave was “ottimo”, which roughly translates to something between “very good” and “excellent”), and he will now be moving to the University of Lisbon as a Della Riccia fellow for his first postdoc - congratulations Tiziano!
Corfu2023 Workshop on Tensions in Cosmology
Straight after the XXV SIGRAV conference, I am travelling to Corfu, Greece, to attend the Corfu2023 Workshop on Tensions in Cosmology. The workshop, as the name suggests, is focused on cosmological tensions, with special attention to the Hubble tension. I have been particularly looking forward to this workshop, firstly because it will be an occasion to catch up with some friends colleagues I haven’t seen in a long time (e.g. Vivian Poulin), and finally meet several people I’ve written many papers with (e.g. Eleonora Di Valentino) or frequently interacted with online (Leandros Perivolaropoulos, Jackson Levi Said, and Özgür Akarsu, to name but a few), but never actually met in person, but also because I’ve never been to Greece before. I will also be delivering a plenary talk on “Seven hints that early-time new physics alone is not sufficient to solve the Hubble tension” (whose slides you can find here), obviously focused on my “seven hints” paper. I look forward to lots of fruitful discussions, and interesting workshop, and a series of exciting social events (including a boat trip and a traditional Greek dinner)!
Media coverage for seven hints paper
My seven hints paper has been picked up by Universe Today, who write a nice piece which you can find here:
www.universetoday.com/163026/its-going-to-take-more-than-early-dark-energy-to-resolve-the-hubble-tension/
The same piece was later picked up by Phys.org. Enjoy the read! 😃
Seven hints that early-time new physics alone is not sufficient to solve the Hubble tension
I’m very excited to share that my latest single-author paper (on which I already gave three talks) has now been published in Universe (in a Special Issue guest edited by Eleonora Di Valentino, Leandros Perivolaropoulos, and Jackson Levi Said)! This is an opinion paper where I argue that the Hubble tension is even nastier than it looks and that, if we insist on it requiring new physics, it will not be enough to add early-time (i.e. pre-recombination) new physics - instead, I present seven reasons in favor of my argument that one should combine early- and late-time new physics, and potentially local new physics as well. The choice of number seven is motivated by Miller’s law, which states that the number of objects the average person can hold in working memory is 7±2. The full bibliographic coordinates for the paper are Universe 9 (2023) 393, and you can also find it in preprint form on arXiv: 2308.16628. Here is a link to the paper (which is published Open Access).
The state of the dark energy equation of state
The dark energy equation of state w is one of the cosmological parameters a number of next-generation surveys aim to measure particularly well, and it is therefore quite surprising that there wasn’t a single paper after the 2003 Melchiorri-Mersini-Ödman-Trodden paper (“The state of the dark energy equation of state”) comprehensively discussing state-of-the-art constraints on w from a number of probes (rather, various papers usually focus on one probe at a time), especially in light of the possible impact of w on cosmological tensions. In today’s new preprint with Luis Escamilla, William Giarè (yes, this was one of the main things William and I worked on during his visit to Trento), Eleonora Di Valentino, and Rafael Nunes, we therefore found it very timely to provide a snapshot of the state of the dark energy equation of state, circa 2023 of course. What we found confirmed a suspicion I have had for a long time, i.e. that current constraints on w (when including data from the CMB) cluster around w~-1.03, and in any case just into the phantom regime. Why is this? We haven’t been able to provide a clear answer, but hopefully you will find some interesting discussions on this and other points in the preprint we just posted on arXiv: 2307.14802.
Tonale Winter School registration open
Registration for the 2023 Tonale Winter School on Cosmology, where I will be lecturing, is now open. Besides cosmological tensions, the other topics covered this year are stochastic gravitational waves backgrounds, full-sky surveys, and the effective field theory of structure formation. Please see the official school page for further details. Only a maximum of 40 participants will be accepted and, given the large number of applications usually received, it is strongly recommended to register as soon as possible. Note that I am not involved in the selection process, so please reach out to the organizers if you have any questions.
Three recent talks
In the past three days I delivered three (online) seminars, all by the title of Seven hints that early-time new physics alone is not sufficient to solve the Hubble tension. I gave the talks “at” IPM, Tehran (Iran); the Institute of Advanced Studies in Science and Technology of Babes-Bolyai University (Romania), within Tiberiu Harko’s highly recommended seminar series in Gravitation, Cosmology, and Astrophysics; and at the conference Recent Advances in Mathematical Sciences and Interdisciplinary Areas 2023 at GLA University (India). I basically reported about a work in progress which I expect will be out in the next three months (so stay tuned!), and all the slides are available on my talks page. A pictorial summary of the work, made by my wife, is shown below.
Tonale Winter School on Cosmology
I’m pleased to announce that I will be lecturing at the Tonale Winter School on Cosmology later this year. This is a well-known cosmology winter school addressed to advanced MSc students, PhD students, and junior postdocs, which started in 2007 and takes place in Passo del Tonale, Italy. I myself attended as a student in 2014. This year I will deliver 4 lectures on cosmological tensions. More details, including the official school page, will follow later!
PhD positions at the University of Trento
The selection for admission to the 39th cycle of the PhD in Physics at the University of Trento is now open, see this link. For interested students not familiar with the procedure, this is done at a centralized (departmental) level, rather than by individual supervisors, through a committee of (typically) four people, which varies each year. There are a total of 22+1 positions, 19+1 of which with scholarship, of which 15+1 on a specific topic and the remaining 4 “free”: since I am not funding any “specific topic” position, students interested in working with me will have to compete for the 4 free fellowships, which means that there is no guarantee I will actually get to have an incoming PhD student this year - note that competition for these free fellowships is typically extremely tough, and it is recommended that if you are interested in working with someone specific, you should explicitly mention this in the cover letter. For a rough guideline on possible topics one could work on with me, please see this link (Section “First call 39° cycle - Other research topics”), and refer to the topics “Dark matter and dark energy in the era of precision multi-messenger cosmology and cosmic tensions (Vagnozzi)” and “Black holes as windows onto fundamental physics (Vagnozzi)” (note, however, that these are not binding). The deadline for applying is May 31 at 16:00 Italy time - please spread the word, and apply if you are interested!
Visit by Leonardo Giani
More visitors! This week we have Leonardo (Leo) Giani, currently a postdoc at the University of Queensland, visiting us for a couple of days. Leo and I are working on a very exciting project, which (spoiler) has to do with Laniakea, our home in the Cosmos, while also discussing other ideas more or less related to dark energy and cosmological tensions. Leo will also be delivering a seminar by the title of “Doctor suggests a new diet for Non-local gravity”. Welcome Leo!
Early dark energy and massive neutrinos paper published in MNRAS!
My paper with Alex Reeves, Laura Herold, Blake Sherwin, and Elisa Ferreira on early dark energy and massive neutrinos, which I previously reported on in an earlier news item, has now officially been published in MNRAS! The full bibliographic coordinates for the paper are Mon. Not. Roy. Astron. Soc. 520 (2023) 3688. Here is a link to the paper.
Visit by Anjan Sen
I’m delighted to host my first official visito here in Trento, Anjan Sen from Jamia Millia Islamia! Anjan is a well-known cosmologist whose recent research interests include the nature of dark energy and cosmological tensions. We have never met in person but have shared many interesting email discussions, and more generally share many common interests among which the cosmological consequences of a negative cosmological constant. Anjan will be visiting us for a week and a half, and will also deliver a seminar by the title of “Story of the Dark Universe”. Looking forward to many interesting discussions!
Early dark energy and massive neutrinos paper accepted in MNRAS!
My paper with Alex Reeves, Laura Herold, Blake Sherwin, and Elisa Ferreira (a very international collaboration, spanning 6 different countries - Switzerland, Germany, Italy, UK, Japan, and Brazil!), where we study whether a cosmological model featuring early dark energy (EDE) and massive neutrinos can alleviate cosmological tensions in a way which bypasses the potential problems EDE faces with galaxy clustering data, has been accepted for publication in MNRAS! We show that the answer is…“yes and no”, in the sense that our paper really reinforces the idea that prior volume effects are very important for EDE, to the extent that some of those which were previously described as problems, just maybe aren’t really problems in the first place. Kudos to Alex and Laura, two outstanding PhD students (though Laura is off to her first postdoc as a Miller fellow at JHU), who did all the heavy-lifting on this paper! It has been quite a journey, considering this paper was born out of Alex’s MSc thesis (Alex did his Part III in Cambridge with me, Blake, and George Efstathiou), whose project was conceived on a stuffy afternoon of July 2020, deep in lockdown period, while the first referee report was humongous to say the least, but really helped improve the paper! You can find the preprint version of the paper on arXiv: 2207.01501.
William Giarè wins STSM grant to visit Trento
We’ll have visitors soon: William Giarè, currently a postdoc at the University of Sheffield, has won a COST short-term scientific mission (STSM) within the CosmoVerse COST Action, which will allow him to visit the University of Trento! COST STSM grants are individual mobility and collaboration grants which are aimed towards fostering collaborations between researchers within a given COST Action. William will be visiting Trento at some point in March, and we plan on finalizing and starting up a number of projects, broadly related to the subject of cosmological tensions, ranging from the nature of dark energy, to the S8 tension “done properly” (I guess you’ll have to wait to see what we mean). We have several interesting things we want to discuss, and I look forward to the visit! Congratulations William!
CosmoVerse
As of today I am officially a member of the CosmoVerse COST (European Cooperation in Science and Technology) Action, an European network of like-minded people with a particular interest in cosmological tensions, aiming at fostering interdisciplinary research. The Action is chaired by Jackson Levi Said at the University of Malta, whereas the Vice Chair is my friend and colleague Eleonora Di Valentino. I look forward to many interesting discussions, workshops, and seminars that will come out of CosmoVerse!
