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.
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!
Negative cosmological constant and JWST paper published in JCAP!
My paper with Shahnawaz Adil, Upala Mukhopadhyay, and Anjan Sen, studying a dark energy model featuring a negative cosmological constant in light of the JWST observations, 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 2310 (2023) 072. Here is a link to the paper (which is published Open Access).
Two recent talks and a visit to Padova
I gave two talks on my works recently, a first one at RWTH Aachen (in the local cosmology plus astroparticle journal club, on my seven hints paper), and a second one at the University of Padova (on “Searching for dark energy off the beaten track”, slides here). The seminar in Padova was actually my first in-person seminar in nearly 4 years, after years of Zoom seminars. It was very nice to visit Padova after many years, and interact with what is probably one of the best (and biggest) cosmology groups in Italy. Both talks were followed by lively discussions which left lots of food for thought (and projects).
Negative cosmological constant and JWST paper accepted in JCAP!
My paper with Shahnawaz Adil, Upala Mukhopadhyay, and Anjan Sen, where we show how a dark energy model featuring a negative cosmological constant with an evolving component on top can potentially explain the puzzling JWST observations (see this earlier news item), has been accepted for publication in JCAP! The revision requested was pretty minor, but a notable (and in my opinion rather important) addition is the new Fig. 1 I produced, where we show the effective equation of state of this dark energy model. In some cases it goes through a singularity, which indicates the point where the total energy density of the dark energy switches sign. The singularity is nothing to worry about, as we argued. You can read the preprint version of the paper on arXiv: 2307.12763.
XXV SIGRAV conference
I’m really excited to be attending the XXV SIGRAV conference of the Italian Society for General Relativity and Gravitation in the beautiful city of Trieste! I will be picking up the 2023 SIGRAV Prize (see this earlier news item) and on the occasion I will also be delivering a plenary talk on “Searching for dark energy off the beaten track” (whose slides you can find here), presenting some of the ideas I’ve been developing over the past years. This is my second in-person conference after the pandemic, but the first which actually required travelling (the previous one took place in Trento). There are lots of people attending whose work I’ve been following for years, or whom I’m working together with or even wrote papers with, but never had the chance to meet in person (just to mention a few, Vitor Cardoso, Che-Yu Chen, Gaetano Lambiase, Gabriele Gionti, and Joe Silk), so I look forward to many interesting discussions!
Internal Call for Research 2023 grant application
I just submitted an application for an UniTrento Internal Call for Research 2023 grant, funded by the Autonomous Province of Trento (PAT). I based my scientific case largely on the ERC StG application I submitted last year, obviously after taking into account reviewer feedback. I should hear back in October and, if successful, this would allow me to hire a couple of postdocs - I’m keeping my fingers crossed!
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.
Negative cosmological constant and JWST observations of high-redshift galaxies
Last summer, early observations from the James Webb Space Telescope (JWST) caused quite a stir due to their discovery of a puzzlingly abundant population of extremely massive galaxies at too high redshift, too many to have been in place if the ΛCDM model as we understand it is correct. In today’s new preprint with Shahnawaz Adil, Upala Mukhopadhyay, and Anjan Sen (all three from JMI, and kudos to Shahnawaz and Upala who did all the heavy-lifting!) we study whether these results could be explained by a dark energy model beyond the cosmological constant. In particular we consider a model featuring a negative cosmological constant (anti de Sitter vacuum) with an evolving component (whose energy density is of course positive) on top - this model is phenomenologically motivated from string theory considerations, particularly the swampland program, and the difficulty in constructing consistent de Sitter string vacua. We show that such a model can dramatically alter structure formation and potentially explain how the galaxies seen by JWST could have been in place much earlier than is allowed within ΛCDM. You can read our results in the preprint we just posted on arXiv: 2307.12763.
Visit by Michael Zantedeschi
This week we have Michael Zantedeschi, currently a postdoc at the Tsung-Dao Lee Institute, Shanghai Jiao Tong University (in the group of Luca Visinelli), visiting us for a couple of days. Michael is actually not new to Trento, having been an undergrad here (although he arrived just after I finished my undergrad, so we never overlapped). While we aren’t directly working together (yet), we will be brainstorming ideas related to screened dark energy, as well as the mysterious cosmological constant. Welcome Michael!
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!
ERC Starting Grant evaluation report
Today I received the evaluation report for Step 1 of my ERC Starting Grant application, which was unsurprisingly unsuccessful - as I promised in an earlier news item, I have decided to openly report the outcome of the evaluation to help normalize otherwise taboo discussions about lack of success in academia. I received a “B” (proposal of high quality but not sufficient to pass to Step 2 of the evaluation), which means I am blocked from applying for a further year. The comments from the 4 reviewers were actually extremely positive (their ratings included 7 “exceptional”, 3 “excellent”, and 2 “very good”), and the high-risk high-gain nature of the project was clearly appreciated. The main issue identified by more than one reviewers was that I probably put too much at once - a subset of the proposal focusing on 2/3 of the ideas I put out there would probably have stood a much better chance. This was a very useful experience, the reviewer comments were very helpful and I have to say somewhat reassuring, so at this point there’s not much more I can do than roll up my sleeves, while looking forward to trying again in 2024 taking this feedback into account!
Visit by William Giarè
This week we have William Giarè visiting us from the University of Sheffield, funded by a CosmoVerse COST STSM grant, as reported in this earlier news item. We’ll be finalizing a project exploring the state of the dark energy equation of state (pun intended), while starting up a number of other projects somewhat broadly related to cosmological tensions and the nature of dark energy. Looking forward to an exciting week of science!
Universe special issue (successfully) closed
The Universe Special Issue “Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches” I guest edited together with Eleonora Di Valentino, Alessandro Melchiorri, Olga Mena, and Luca Visinelli, has officially closed today. I am happy say that it was a great success: we published 21 papers, some of which either already of very high impact, or whose impact I expect will be very high. Some highlights of the Special Issue include the classic Mazur-Mottola 2001 gravastar paper (with nearly 1000 citations!), which had previously remained unpublished for over two decades, with a similar fate for the classic Benaoum 2002 modified Chaplygin gas paper, and finally a nice review on dark radiation by Archidiacono and Gariazzo. It was a great fun to work on this Special Issue, and thanks to all the authors for their very nice contributions!
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!
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!