My two papers on primordial regular BHs with Marco Calzà and Davide Pedrotti (see these two earlier news items: part 1 and part 2), where we characterize non-singular primordial BHs as DM candidates, have now officially been published in PRD! The full bibliographic coordinates for the papers are Phys. Rev. D 111 (2025) 024009 and Phys. Rev. D 111 (2025) 042010. Here and here are the links to the papers.
Hubble tension, Ωm, and ωc paper published in PRD!
My paper with Davide Pedrotti, Jun-Qian Jiang, Luis Escamilla, and Simony Santos da Costa, where we discuss the multidimensionality of the Hubble tension and the roles of Ωm and ωc (see this earlier news item), has now officially been published in PRD! The full bibliographic coordinates for the paper are Phys. Rev. D 111 (2025) 023506. Here is the link to the paper.
Hubble tension, Ωm, and ωc paper accepted in PRD!
My paper with Davide Pedrotti, Jun-Qian Jiang, Luis Escamilla, and Simony Santos da Costa, where we discuss the multidimensionality of the Hubble tension and the roles of Ωm and ωc (see this earlier news item), has been accepted for publication in PRD! There were extremely minor revisions compared to the earlier version, which have resulted in a clearer discussion of the novel aspects and the domain of applicability of our results. You can read the preprint version of the paper on arXiv: 2408.04530.
Primordial regular black holes papers accepted in PRD!
Extremely good news today as my two earlier papers on primordial regular BHs with Marco Calzà and Davide Pedrotti (see these two earlier news items: part 1 and part 2), where we characterize non-singular primordial BHs as DM candidates, have both been accepted for publication in PRD! There have been a few changes with respect to the earlier versions (slight changes to the titles, discussions on the time evolution of these BHs added, and a few minor additions), but our main messages are unaltered. You can read the preprint versions of the papers on arXiv: 2409.02804 and 2409.02807.
Fifth forces and Bennu paper mentioned in Scientific American
A recent piece in Scientific American, mainly focused on this recent paper on tests of asteroid-mass primordial black holes from Solar System ephemerides, dedicated a paragraph to our recent paper in Communications Physics on using the asteroid Bennu to test dark matter and other aspects of fundamental physics (see this earlier news item), with quotes from first author Yu-Dai Tsai. Here is a link to the piece in Scientific American:
www.scientificamerican.com/article/dark-matter-black-holes-could-fly-through-the-solar-system-once-a-decade/
Fifth forces and Bennu paper published in Communications Physics!
My paper with Yu-Dai Tsai, Davide Farnocchia, Marco Micheli, and Luca Visinelli, where we use OSIRIS-REx tracking data for the asteroid Bennu to set new constraints on fifth forces and ultralight dark matter (see this earlier news item), has now officially been published in Communications Physics (making this my first proper Nature publication)! The full bibliographic coordinates for the paper are Commun. Phys. 7 (2024) 311. Here is the link to the paper (which is published Open Access).
Primordial regular black holes (part 2)
A truly busy day today, as with Marco Calzà and Davide Pedrotti we posted not one but two papers! In our first paper, covered in this other news item and motivated by the fact that all studies on primordial black holes (PBHs) consider Schwarzschild and Kerr BHs which feature curvature singularities, we took a first step towards studying primordial regular BHs as dark matter (DM) candidates, focusing on phenomenological tr-symmetric metrics. In this paper, we extend our pilot study to non-tr-symmetric metrics, which complicate our work by a fair margin. Aside from the well-known Simpson-Visser metric, the space-times we studied include two metrics inspired by Loop Quantum Gravity, more specifically the Peltola-Kunstatter and D’Ambrosio-Rovelli ones, and in all three cases we find that the “asteroid mass window” where all the DM can be made of PBHs is enlarged. You can read our results in the preprint we just posted on arXiv: 2409.02807.
Primordial regular black holes (part 1)
I would be lying if I didn’t say I am particularly proud of this new paper which appeared today with Marco Calzà and Davide Pedrotti, making it another made in Trentino paper and, especially, another paper entirely produced within my group (note that this paper is for 2/3 made within the Valle dei Laghi, which is where both Marco and Davide originally come from)! There are a huge number of studies on primordial black holes (PBHs) as potential dark matter (DM) candidates, yet virtually (almost) all of these works consider Schwarzschild or Kerr BHs, which suffer from a few well-known problems, including the presence of curvature singularities. In today’s paper we therefore took a first step towards characterizing primordial regular BHs (which, on the contrary, do not feature curvature singularities) as DM candidates, finding that they can potentially lead to a larger “asteroid mass window” where PBHs can make up all the DM. Today’s pilot study is focused on so-called tr-symmetric metrics, which include the well-known Bardeen and Hayward regular BHs, whereas we have also put out a companion paper (covered in this other news item), where we study non-tr-symmetric metrics, which also include metrics inspired from Loop Quantum Gravity. You can read our results in the preprint we just posted on arXiv: 2409.02804.
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.
Visit by Luca Visinelli
We are delighted to have Luca Visinelli visiting us once more! Luca is a Professor at the Tsung-Dao Lee Insittute in Shanghai Jiao Tong University: he is a very well-known scientist with broad research interests spanning dark matter, dark energy, and black holes. It was a very enjoyable visit during which we took the opportunity to catch up on our ongoing projects (especially replying to pending referee reports!) and enjoy the surroundings of Povo, while Luca also gave a seminar by the title of “Theoretical motivations for a light boson and its phenomenology”.
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!
Visit by Françoise Combes
For the next two days we have the pleasure of hosting Prof. Françoise Combes, a renown astrophysicist from Collège de France. Françoise is here as visiting chair within the University of Trento-College de France exchange program for Professors. She will be delivering a seminar by the title of “Black Holes and Active Galaxy Nuclei” and a colloquium by the title of “The Puzzle of Dark Matter”. With the rest of our group we had a nice lunch together at Orostube in Povo, where the carbonara pizza I ate was particularly good and worthy of a picture! Welcome Françoise!
Constraints on fifth forces from OSIRIS-REx tracking data for Bennu
Really excited about the new preprint we just posted with Yu-Dai Tsai, Davide Farnocchia, Marco Micheli, and Luca Visinelli, where we use OSIRIS-REx tracking data for the asteroid Bennu to set new constraints on fifth forces and ultralight dark matter - in certain ranges of mediator mass these are among the tightest constraints ever obtained! This is a follow-up to our earlier paper in JCAP where we only considered the effect of such particles on the asteroid orbital precession. In our new preprint we are instead using real tracking data from the OSIRIS-REx mission and ground-based optical and radar telescopes, gathering as much information as possible on Bennu’s full trajectory. The timing is, to say the least, perfect, as in the past days OSIRIS-REx has been making headlines, being on its way back to Earth with a sample of Bennu. You can read our results in the preprint we just posted on arXiv: 2309.13106.
Visit by Anish Ghoshal
This week we have Anish Ghoshal, currently a postdoc at the University of Warsaw, visiting us for a couple of days. Anish is visiting to work on a couple of projects both with me and Max Rinaldi, respectively on novel dark matter production mechanisms, and inflation. Welcome Anish!
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!
Asteroid and fifth forces paper published in JCAP!
My paper with Yu-Dai Tsai, Youjia Wu, and Luca Visinelli on the use of asteroids as a probe of fifth forces, 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 2304 (2023) 031. Here is the link to the paper.
Asteroid precession and fifth forces paper accepted in JCAP!
My paper with Yu-Dai Tsai, Youjia Wu, and Luca Visinelli, where we use asteroids as a probe of fifth forces, including those mediated by new ultralight particles which could be the dark matter, has been accepted for publication in JCAP! We find that we can potentially set some of the leading fifth force constraints in a certain range of mediator mass. This is another paper which has gone through a really long journey, as it was conceived during a brainstorm Zoom call in October 2020. We are now developing a number of follow-up ideas with asteroid experts, so stay tuned for more! You can find the preprint version of the paper on arXiv: 2107.04038.
Visit by Luca Visinelli
And we have more visitors: Luca Visinelli from Shanghai Jiao Tong University will also be here for the next two days! Luca is a close collaborator of mine (he is in fact the person with whom I have the most papers in common, with the reverse also holding), and is a very well-known scientist with broad research interests spanning dark matter, dark energy, and black holes. We’ll take the opportunity to catch up on the many projects we have ongoing, and Luca will also deliver a seminar by the title of “The interplay of primordial black holes and particle dark matter”. To celebrate Luca’s birthday, we enjoyed a nice dinner together with Anjan (see below) at La Grotta, one of my favorite restaurants in Trento. It’s very nice to have people travelling and visiting once more, it was definitely something I had missed during the pandemic!
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!
