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.
Davide Pedrotti's MSc defense
Congratulations to Davide Pedrotti, who today successfully defended his MSc thesis, by the title of “Studies on Quasi-Normal Modes and Shadows of Black Holes” (with the opponent being Prof. Albino Perego)! Davide’s defense was outstanding (one of the committee members, a condensed matter physicist, said: “This is the first talk on black holes I’ve understood in years”), and in fact he received top grades and honours, i.e. 110 e Lode. In his thesis, supervised by myself and Prof. Kostas Kokkotas at the University of Tübingen, Davide studied quasi-normal modes and shadows of a number of well-motivated BH metrics beyond GR, and in particular investigated the non-trivial correspondence between the two for metrics describing rotating regular BHs: part of his thesis will be written up in a paper in the coming months, so stay tuned! During the same day, I also served as opponent for an MSc student of Prof. Bill Weber. Davide will now be enjoying a few days of deserved break before starting hiw new adventure as a PhD student in Trento in November.
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).
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.
