We’re excited to welcome our latest visitor: Francesco Di Filippo from Charles University in Prague! Francesco, hosted by Max Rinaldi, is currently a postdoc at Charles University in Prague, where he has been doing a lot of interesting work especially on regular black holes and possible instabilities (or not) thereof, together with a bunch of experts in the field including Stefano Liberati and Matt Visser - he will be delivering a seminar at TIFPA by the title of “Non-singular black holes: Open issues and implications”. Welcome Francesco!
Quasinormal modes-shadow correspondence for rotating regular black holes
I’m truly thrilled to see my latest preprint with my PhD student Davide Pedrotti, which also happens to be Davide’s first paper, out on arXiv! This work is the one I was anticipating in an earlier news item, and is based on part of Davide’s MSc thesis - so, needless to say, kudos to Davide who did all the hard work! There is a well-known correspondence between black hole quasinormal modes (QNMs) in the eikonal limit (ℓ>>1), and the size of BH shadows: this correspondence has been extensively studied for spherically symmetric space-times, but the extension to rotating space-times is non-trivial, and has only been worked out either only for equatorial QNMs (m=±ℓ), or for general QNMs but limited to the Kerr metric. What we did with Davide was to extend this correspondence to more general rotating space-times, then testing it explicitly on the rotating regular Bardeen and Hayward BHs, while also discussing the conditions under which the correspondence holds within general rotating space-times (basically the Hamilton-Jacobi and Klein-Gordon equations have to be separable). You can read our results in the preprint we just posted on arXiv (with what I think is a pretty cool title): 2404.07589.
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!
Marco Calzà joins my group!
I’m really excited to welcome the first postdoc in my group! Today Marco Calzà joins my group as one of the 2 DARKTRACK-funded postdocs (of the two, the BH theorist). Marco did his PhD at the University of Coimbra under the supervision of João Rosa, working on a bunch of very interesting things BH-related, from superradiance to evaporation. His expertise and interests were simply a perfect fit for what I plan on doing within DARKTRACK, and I really look forward to working together. Welcome Marco (or, to be more precise, welcome back, since he was actually a BSc and MSc student here in Trento some years ago)!
Sgr A* horizon-scale tests paper published in CQG!
My paper with Rittick Roy, Yu-Dai Tsai, Luca Visinelli, Misba Afrin, Alireza Allahyari, Parth Bambhaniya, Dipanjan Dey, Sushant Ghosh, Pankaj Joshi, Kimet Jusufi, Mohsen Khodadi, Rahul Kumar Walia, Ali Övgün, and Cosimo Bambi on horizon-scale tests of gravity theories and fundamental physics from the EHT image of Sgr A*, which I previously reported on in an earlier news item, has now officially been published in CQG! The full bibliographic coordinates for the paper are Class. Quant. Grav. 40 (2023) 165007. Here is a link to the paper (which is published Open Access).
Sgr A* horizon-scale tests paper accepted in CQG!
I’m really excited that my paper on horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope (EHT) image of Sagittarius A* (Sgr A*) has been accepted for publication in CQG! This is a huge paper I led with 14 other authors spread throughout the world (our countries of affiliation include Italy, UK, China, USA, India, Iran, Canada, South Africa, North Macedonia, and Turkey): Rittick Roy, Yu-Dai Tsai, Luca Visinelli, Misba Afrin, Alireza Allahyari, Parth Bambhaniya, Dipanjan Dey, Sushant Ghosh, Pankaj Joshi, Kimet Jusufi, Mohsen Khodadi, Rahul Kumar Walia, Ali Övgün, and Cosimo Bambi. We used the EHT image of Sgr A* to test over 50 well-motivated theoretical scenarios, ranging from theories of gravity, novel fundamental physics frameworks, and black hole mimickers such as naked singularities and wormholes. This paper was initially (see v1) written only with Rittick, Yu-Dai, and Luca, tirelessly and also shamelessly ambulance-chased over a weekend following the exciting EHT announcement on May 12, 2022, but was then substantially polished and extended throughout summer 2022 with the addition of all the new authors - it is easily one of the most impactful papers I’ve ever written and at the same time likely the paper that drained the most energy out of me, and I’m really relieved to finally see it accepted for publication, after a very long refereeing process (one of the referee reports was a 4-page long pdf in 10pt font!). You can find the preprint version of the paper on arXiv: 2205.07787.
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!
LQG and Sgr A* paper published in ApJ!
My paper with Misba Afrin and Sushant Ghosh on Loop Quantum Gravity and the shadow of Sgr A*, which I previously reported on in an earlier news item, has now officially been published in ApJ! The full bibliographic coordinates for the paper are Astrophys. J. 944 (2023) 149. Here is a link to the paper (which is published Open Access).
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!
LQG and Sgr A* paper accepted in ApJ!
The year is off to a truly great start research-wise: my paper with Misba Afrin and Sushant Ghosh, where we test two Loop Quantum Gravity (LQG, which is an interesting candidate framework for quantum gravity)-inspired rotating black hole space-times against the Event Horizon Telescope image of Sgr A*, the black hole at the center of our galaxy, has just been accepted for publication in ApJ! We use the size and shape of the shadow to place limits on a parameter which basically quantifies the strength of LQG effects. Our bounds are of course comparatively weak, but at the same time are interesting as a proof of principle given that there are very few ways (if any at all!) to test LQG from the observational point of view. And kudos to Misba, an outstanding PhD student at Jamia Millia Islamia, who did basically all the heavy-lifting on this paper! You can find the preprint version of the paper on arXiv: 2209.12584.
New (first) group member!
Today Davide Pedrotti joins my group as a new Master’s student. Davide is enrolled in the Trento-Tübingen Double Degree, and will be jointly supervised by me in Trento, and by Prof. Kostas Kokkotas in Tübingen. While the finer details remain to be defined, Davide’s thesis will be on the topic of quasi-normal modes of black holes beyond GR, their use in testing gravity, and potentially their connection to black hole shadows. Welcome Davide, and looking forward to our work together!