June 6, 2023
Happy to report we got a grant from the Italian PRIN program! This is in collaboration with Andrea Maselli from GSSI in L’Aquila. The title is “Gravitational-wave astronomy as a mature field: characterizing selection biases and environmental effects”. Stay tuned for more research (and more positions to join our group!).
May 30, 2023
We do population analysis in gravitational waves all the time now. That is: we compare many observations from GW experiments against many simulated datapoints from simulations. But what if you only have one observation? That could be a LIGO guy that is kind of an outlier (think GW190521) or maybe a datapoint from a future detector (think LISA) that feels lonely in his parameter space. Don’t look further, this is stats for you (and Matt’s last paper as a grad student…)
Matthew Mould, Davide Gerosa, Marco Dall’Amico, Michela Mapelli.
arXiv:2305.18539 [astro-ph.HE].
May 17, 2023
We’ve got the best name ever for a numerical code! Let me introduce QLUSTER which, guess what, simulates clusters. We finally put out a piece of code that was originally developed in 2019 and later used in several papers. It’s a very very simple treatment of black-hole binary formation in dense stellar environments, with the goal of predicting gravitational waves from repeated mergers. The code is available at github.com/mdmould/qluster and a short description is provided in the proceedings of the 2023 edition of the amazing Moriond conference.
Davide Gerosa, Matthew Mould.
arXiv:2305.04987 [astro-ph.HE].
April 27, 2023
This paper is episode four in the up-down instability series. We first figured out the instability exists (episode 1), then computed when binaries go after the instability (i.e. the endpoint, episode 2), and also checked binaries are really unstable in numerical relativity (episode 3). Now we look at the inference problem with LIGO/Virgo: if unstable up-down binaries enter the sensitivity window of the detector, will we be able to tell? We phrased the problem with some fancy stats using the so-called Savage Dickey density ratio, which is the right tool to answer this question. As is too often the case, current data are not informative enough but the future is bright and loud.
Viola De Renzis, Davide Gerosa, Matthew Mould, Riccardo Buscicchio, Lorenzo Zanga.
arXiv:2304.13063 [gr-qc].
April 12, 2023
It’s out! The notorious (ask my students…) “precession v2” paper is finally out! This took a veeeery long time; we checked and the first commit for this paper is from May 2020 (!). But the result is an exhilarating tour of spin precession at 2PN with 27 pages and 183 (!!!) numbered equations. We rewrote the entire formalism, change how we parametrize things, compute all we could in closed forms, and speed up the computational implementation. It’s cool, now performing a precession-averaged evolution is a <0.1s operation. If you’re into BH binary spin precession, this is the paper for you. All of this is now part v2 of our PRECESSION python module. So long, and thanks for all the spin.
Davide Gerosa, Giulia Fumagalli, Matthew Mould, Giovanni Cavallotto, Diego Padilla Monroy, Daria Gangardt, Viola De Renzis.
arXiv:2304.04801 [gr-qc].
Open-source code: homepage, repository, documentation.
March 29, 2023
Third-generation gravitational wave detectors are going to see all stellar-mass black-hole mergers in the Universe. Wooooooooo. But hang on, is this enough? Observing the sources is great, but then we need to measure them. Here we try to focus on the latter and quantify how well we will be able to measure the distance of black holes. Read the paper now, but the short answer is that 3G detectors are going to be awesome but not that awesome…
Michele Mancarella, Francesco Iacovelli, Davide Gerosa.
arXiv:2303.16323 [gr-qc].
March 23, 2023
The University of Milano-Bicocca welcomes applications for PhD scholarships. The application deadline is April 19th, 2023 for positions starting in the Fall of 2023:
In particular, the theoretical astrophysics group is looking for highly motivated candidates to join our activities in black-hole binary dynamics, gravitational-wave data exploitation, and numerical relativity. Faculty members with matching interests include Gerosa, Sesana, Colpi, Dotti, and Giacomazzo. Candidates will have ample opportunities to work with and visit external collaborators as well.
Our PhD admission program includes a number of “open” scholarships, covering all research activities in the department (including ours!). All candidates are considered for those by default. In addition, our group this year is advertising an additional “project” scholarship titled “Gravitational-wave source modeling” and supervised by Gerosa. Candidates wishing to be considered for this additional opportunity should indicate it explicitly when applying (the number of this position FIS.3).
We strive to build an inclusive group and welcome applications from all interested candidates. More information on the astrophysics group at Bicocca can be found at astro.fisica.unimib.it. For informal inquiries and expressions of interest please do not hesitate to contact [email protected]
March 22, 2023
It’s student time! Massive congratulations to two of my students who just graduated.
The star of the day is Matteo Boschini, who completed his MSc project with me after a long visit at the AEI (Postdam, Germany) to collaborate with Vijay Varma. Matteo worked out an amazing extension of current numerical-relativity surrogate models… stay tuned for a paper because this is going to be cool!
Daniele Chirico completed his BSc studies with a sweet research project on supernova explosions, orbits, and kicks. He’s staying in Milan for his MSc degree now, so wait a bit for his successes!
February 28, 2023
I’m about to start teaching this year’s edition of “Astrostatistics and Machine Learning” for the MSc degree in Astrophysics here at Milano-Bicocca. The material is available at
github.com/dgerosa/astrostatistics_bicocca_2023
Feel free to have a look if you fancy some stats… and please do send me feedback if you work through the material.
February 27, 2023
The student reps of our department (codename: redshift) have organized a stellar event today. Curiosity and interest in the LISA space mission brought them to design a full day of talks from leading experts in the field. They put Stefano Vitale, Alessandra Buonanno, and Bernard Schutz in the same room with the (astro)physics students and, well, a few of us who tagged along. The result was an amazing rollercoaster called “LISA and beyond” across the wonders of the experimental design by Stefano (is this truly going to work?!?), some amazing order-of-magnitude calculations that Bernard pulled off (wish I could do that!), and a broad vision by Alessandra across the discoveries we had and those we will soon be seeing (can’t wait, can’t wait!). Our students engaged with the speakers, asked questions, and organized a round table touching topics like the carbon footprint of space missions, gender equality, and how to manage a research group. Such ingenuity and enthusiasm are what keeps science alive! We should learn from our students and do science like that.
January 12, 2023
It is a pleasure to announce the workshop “Gravitational-wave populations: what’s next?” which we are currently organizing for next summer:
https://sites.google.com/unimib.it/gwpopnext
As the catalog of detected gravitational-wave events grows from O(10) to O(100) sources (but think millions in a few decades!), such increasingly detailed information is allowing us to dig deeper into the (astro)physics of compact objects. At the same time, new and more data require appropriately powerful statistical tools to be fully exploited. This highly interactive workshop (fewer talks, more working together!) will be the opportunity to share recent progress, identify what new steps are now needed, and hopefully set the stage for substantial progress in the field.
The workshop will take place on July 10-14, 2023 at the University of Milano-Bicocca, which is located near the city center of Milan, Italy. Milan is a beautiful, international city in the north of Italy and is served by three major airports with worldwide connections. The city is home to art, history, and great food; nearby excursions will take you to the Italian lakes and the stunning Alps.
While we are unable to provide travel support, the workshop will have no registration fee. The workshop will be in person without remote options.
Interested participants should register on the conference website by March 1st, 2023. Depending on the number of people registering, participants might need to be selected. We will be in touch soon after the registration deadline, so please do not make travel plans until you hear back from us. When registering please indicate which of the discussion session(s) you would like to contribute to. Early career scientists will have the opportunity to give flash talks highlighting their science.
Davide Gerosa (Milano-Bicocca), Emanuele Berti (Johns Hopkins), Salvatore Vitale (MIT)
January 1, 2023
Welcome to 2023… and what better way to start the new year than welcoming a new friend! Alice Spadaro (who has recently graduated with an MSc degree here in Milan) is now officially starting her PhD in my group. Alice always smiles, likes surfing, and of course is into gravitational waves 🙂 .
November 21, 2022
Huge congrats to two of my students who graduated today! Matteo Muriano completed a funny BSc project on black-hole merger trees. And Giovanni Cavallotto went all in for his MSc research: he basically “fixed” black-hole binary spin precession at 2PN! (which is pretty cool, stay tuned for these results!). They both defended quite brilliantly, good luck with everything now!
November 15, 2022
We want more! With gravitational-wave data, some quantities like the masses of the black holes are much easier to see than others. But those others are very interesting, notably spins that process and orbits that are eccentric, because they would tell us how black hole binaries came to be in the first place. So while it would be great to see those, it’s also being very hard. Some tentative claims have been made with current data, but nothing unambiguous so far. In this paper led by Isobel from Cambridge, we show that (surprise surprise…) the signals needs to be long enough before one can tell eccentricity and spin precession apart.
Isobel Romero-Shaw, Davide Gerosa, Nicholas Loutrel.
Monthly Notices of the Royal Astronomical Society 519 (2023) 5352–5357.
arXiv:2211.07528 [astro-ph.HE].
November 2, 2022
Together with my postdoc Nate, we’re proceeding our investigations on supermassive, spinning binary black holes surrounded by accretion disks (that is: a ton of gas around big monsters at the center of galaxies!). In today’s paper, we dig a bit deeper into what happens when the disk breaks. That presumably stops the interactions between the gas and the black-hole spins which could make all this funky astrophysics (spins that moves, disks that breaks, etc) actually observable with future gravitational-wave detectors. More needs to be done of course, but here we are.
Nathan Steinle, Davide Gerosa.
Monthly Notices of the Royal Astronomical Society 519 (2023) 5031–5042.
arXiv:2211.00044 [astro-ph.HE].
October 25, 2022
More graduations today! I had the pleasure to see three of my students defending their scientific work. Lorenzo Zanga completed his BSc project on unstable spinning black-hole binaries, Alessandro Carzaniga defended his MSc thesis on gaussianities in the LISA detector, and Alice Spadaro also presented her MSc-thesis work on the LISA mock data challenge. It’s so great to see students reaching the point of defending/arguing/explaining their science… I think it’s actually one of the best things about my job! Thank you all for sharing these months with me, I’ll see you around! (And thanks to Viola De Renzis and Riccardo Buscicchio who co-supervised Lorenzo, Alessandro, and Alice with me).
October 13, 2022
My group is hosting quite a few visitors this semester. We’re alive!
October 12, 2022
So many new people are joining us this Fall!
Welcome everybody, it’s an honor you decided to do science with us! You can read their profiles here. And if you’re also interested in my group, we have multiple openings right now. Consider applying!
September 29, 2022
The University of Milano-Bicocca (Italy) invites expressions of interest for postdoctoral positions in gravitational-wave astronomy.
Successful candidates will join the group of Prof. Davide Gerosa and will be part of the “GWmining” project funded by the European Research Council. Targeted investigations focus on the astrophysical exploitation of gravitational-wave data. We are particularly interested in candidates with expertise in population-synthesis simulations of compact binaries, gravitational-wave parameter estimation and population studies, and numerical-relativity surrogate modeling (although we are open to all candidates with a strong gravitational-wave and/or high-energy astrophysics background!). Candidates will have ample opportunities to collaborate and kickstart new projects with group members and will be strongly encouraged to develop their own independent collaborations.
We anticipate awarding up to three positions. Appointments will be for a three-year term and come with generous research and travel budget. The starting date is negotiable.
The astrophysics group at Milano-Bicocca provides a vibrant environment with expertise covering all aspects of gravitational-wave astronomy, relativistic astrophysics, and numerical relativity, as well as a wider astronomical context including observational and experimental activities. The group has tight connections with the LISA Consortium, the Virgo Collaboration, the Einstein Telescope Observational Science Board, the Italian National Institute for Nuclear Physics (INFN), and the newly formed Italian Center for Supercomputing (ICSC). Faculty members with matching interests include Gerosa, Sesana, Colpi, Giacomazzo, and Dotti. For more information on Gerosa’s group see https://davidegerosa.com/group
Milan is a beautiful, international city in the north of Italy with history, art, and outstanding food. Mountains and lakes are just around the corner.
Successful candidates will have a PhD in Physics or related discipline, strong programming skills, and previous experience in gravitational (astro)physics. Applications should include a CV with a list of publications and a two-page statement covering research interests and plans. These should be sent by November 18th, 2022 using this web form:
https://forms.gle/hnQc3N1xh53YAziH9
Candidates should also arrange for at least two, but preferably three, reference letters to be sent using the same form by November 18th, 2022.
We strive to build a diverse and inclusive environment and welcome expressions of interest from traditionally underrepresented groups.
For inquiries please do not hesitate to contact Davide Gerosa at [email protected].
September 21, 2022
Wooo! What an amazing performance by two of my students today, who defended their BSc and MSc degrees! Oliver Rossi discussed his BSc project on black holes with large spins completed in collaboration with Viola De Renzis (PhD student in my group). Andrea Geminardi presented the results of his MSc thesis. Andrea studied the stochastic gravitational-wave background with myself, Riccardo Buscicchio (postdoc here in Milan), and Arianna Renzini (postdoc at Caltech). Hope you guys had fun working with us, we certainly did! (and I’m sorry for my pain-in-the-*** comments on your plots…). All the best for what comes next!
September 19, 2022
The Italian government has pushed a hiring program dedicated to holders and applicants of Marie Curie Fellowships from the EU. The call targets those that have either (i) completed a successful Marie Curie Fellowship in the past 4 years or (ii) applied unsuccessfully in the past 4 years but were awarded the so-called “Seal of Excellence”.
For both categories, successful candidates will be awarded a 3yr senior researcher position (at the so-called RTDA level in the Italian system). RTDAs are hired as full employees with related benefits and have limited teaching duties. On top of this, candidates in the Marie Curie winners strand (i) will also be offered a substantial startup grant to hire their own PhD students and postdocs.
All Italian institutions can act as hosts, so I encourage you to contact one of us in the country for more information.
In particular, the gravitational-wave group at the University of Milano-Bicocca provides a vibrant environment with activities ranging from relativistic astrophysics. gravitational-wave data analysis, numerical relativity, and gravity theory. The group counts faculty members Gerosa, Sesana, Colpi, Giacomazzo, and Dotti as well as tens of students and postdocs. The city of Milan is a jewel in the north of Italy with a charming international vibe (as well as mountains, history, art, and outstanding food).
The internal application deadline is October 18th. If you’re eligible and/or interested in applying with us, please get in touch asap ([email protected]) and we’ll go from there.
Here are the relevant webpages (scroll down for the English text):
(i) Marie Curie past winners
(ii) Seal of Excellence holders:
August 30, 2022
The Italian government is pushing a major inverstment program in High-Performance Computing, and we’re part of it! The new ICSC (Italian Center for Supercomputing) will manage >300M Euros going towards early-career researchers, PhD scholarships, and computing infrastructure. The University of Milano-Bicocca is part of the founding member of ICSC, with our research group providing some core activities for the Bicocca contribution. If you’re interested in computational (astro)physics, stay tuned for several upcoming opportunities!
July 4, 2022
Lots of “firsts” today! My first-year PhD student Viola just put out her first first-author paper. This is about measuring black holes with not one, but two precessing spins. People have been trying to figure out how to tell if at least one of the two spins of a merging black-hole binary is precessing for quite some time now. And maybe we’ve even done it already for one or two of the current LIGO-Virgo events. But here I must quote that epic Italian commercial from the 90s: “two gust is megl che one” (which is a terrible Italian-English mishmash on a terrible joke to say that when you eat a Maxibon “two flavors are better than one”). In this paper we propose a strategy to identify sources that have the strongest evidence of two processing spins. Viola has been putting together simulated data for the next LIGO/Virgo data-taking period, and the result is pretty cool. If these binaries are out there in the Universe, we will be able to tell they have two spins going around!
Viola De Renzis, Davide Gerosa, Geraint Pratten, Patricia Schmidt, Matthew Mould.
Physical Review D 106 (2022) 084040.
arXiv:2207.00030 [gr-qc].
June 1, 2022
We’re having four (!) summer students joining the group this year!
Welcome all! We look forward to seeing your summer discoveries!
May 25, 2022
Big stars burn everything they have, die fast, and produce big black holes. So when you see two black holes together, it’s likely that the big black hole comes from the big star. Or maybe not? Before dying, the big star can drop some mass onto the other guy, making it bigger! So now, the initially big star still produces the first black hole, but, at the end of the day, that might not be the more massive black hole anymore! This scenario is called “mass-ratio reversal” and our astrophysics friends have put together many models out there showing this is indeed possible for a good fraction of the black holes that produce gravitational-wave events. So here we ask the data: given the events LIGO and Virgo have seen so far, what’s the evidence for mass-ratio reversal in binary stars? Read Matt’s paper to find out.
Matthew Mould, Davide Gerosa, Floor S. Broekgaarden, Nathan Steinle.
Monthly Notices of the Royal Astronomical Society 517 (2022) 2738–2745.
arXiv:2205.12329 [astro-ph.HE].
May 4, 2022
Another short post today, but it’s not just astrophysics that will be awesome with LISA, but fundamental physics too! Here is the white paper of the relevant LISA working group. Get ready to test your wildest ideas, my theory friend!
K. G. Arun, et al. (141 authors incl. Davide Gerosa)
arXiv:2205.01597 [gr-qc].
April 26, 2022
The University of Milano-Bicocca welcomes applications for Ph.D. scholarships. The application deadline is May 20th, 2022 for positions starting in the Fall of 2022:
In particular, the theoretical astrophysics group is looking for strong, highly motivated candidates to join our activities in black-hole binary dynamics, gravitational-wave data exploitation, and numerical relativity. Faculty members with matching interests include Gerosa, Sesana, Colpi, Dotti, and Giacomazzo. The candidates will have ample opportunities to work with and visit external collaborators as well.
Our PhD admission program includes a number of “open” scholarships, covering all research activities in the department (including ours!). All candidates are considered for those by default. In addition, our group sponsors two specific positions:
Candidates wishing to be considered for these additional positions should mention it explicitly in their application.
More information on the astrophysics group at Bicocca can be found at astro.fisica.unimib.it. For informal inquiries please do not hesitate to contact [email protected] or [email protected].
April 22, 2022
The University of Milano-Bicocca (Italy) invites expressions of interest for a 3+2 year research position in HPC applications to astrophysics.
The astrophysics group at Milano-Bicocca provides a vibrant environment with expertise covering all aspects of gravitational-wave astronomy, relativistic astrophysics, galactic dynamics, and numerical relativity. This is embedded in a wider astronomical context including both observational and experimental activities. Our group has tight connections with the LISA Consortium, the Virgo Collaboration, the Einstein Telescope Science Board, the European Pulsar Timing Array, and the Italian National Institute for Nuclear Physics (INFN) via the TEONGRAV national initiative. Staff members with matching interests include Colpi, Dotti, Gerosa, Giacomazzo, Lupi, and Sesana.
Milan is a beautiful, international city in the north of Italy. Mountains and lakes are just around the corner. Art, culture, and food are outstanding. The city hosts three international airports with worldwide connections.
This recruitment campaign is part of a wider national initiative supporting HPC-related computational activities throughout the country. This is a major investment program directly supported by the European Union. It will provide the most ideal context for ambitious candidates wishing to develop and apply state-of-the-art computational and machine-learning tools to current astrophysical and gravitational-wave modeling issues.
The researcher will be appointed at the so-called “RTDA” level for 3 years. The contract can also be extended for 2 more years depending on funding availability. The starting date is negotiable, with the earliest and latest dates on January 1st, 2023 and May 1st, 2023, respectively. RTDA researchers are full-time university employees (with full benefits, such as health insurance and pension plan), have limited teaching duties, and are eligible to fully supervise research MSc student projects. This is an ideal setup for early-career researchers wishing to transition toward research independence and start developing their own group.
The successful candidate will have a PhD in Physics, Astronomy, Computer Science, or related discipline, strong programming skills, and previous experience in one or more of the following topics: HPC workflows, GPU software development, computational astrophysics, gravitational-wave astronomy, numerical relativity, statistical data analysis, machine learning.
Applications should include a CV with a list of publications and a two-page statement covering research interests and plans. These should be sent to [email protected] by June 15th, 2022 for full consideration. Candidates should also arrange for two reference letters to be sent to [email protected] by June 15th, 2022.
We strive to build a diverse and inclusive environment and welcome expressions of interest from traditionally underrepresented groups. Women are especially encouraged to apply. For inquiries please do not hesitate to contact Bruno Giacomazzo ([email protected]) or Davide Gerosa ([email protected]).
April 21, 2022
I was just awarded a large allocation on the Italian national supercomputer at CINECA. My PhD student Viola De Renzis (our parameter-estimation expert!) is the co-I on our proposal. Our award is part of the so-called ISCRA Class B program (which is their medium-size allocation scheme) and amounts to 1.2M CPUh on the Galileo cluster (that is: we’re going to have to crunch a ton of numbers now!). Viola and I will study the extraction of spin-spin couplings from black-hole binaries using gravitational-wave data and stochastic sampling techniques. Stay tuned!
April 13, 2022
We’re at Johns Hopkins University (Baltimore) today, for a brainstorming workshop we organized together with the gravity groups at JHU and Penn State. A ton of interesting people, cool science, fun numerics, big black holes, future detectors, and many new exciting projects we all want to start. The idea is to get “a little help from my (gravity) friends”. Have a look at what we’re up to: davidegerosa.com/with-a-little-help-from-my-friends-workshop/
April 8, 2022
Observing gravitational waves from the ground (i.e. LIGO, Virgo, etc) give us a unique view on “the last three minutes” of the life of compact objects before they merge with each other. Going to space (I’m talking to you, LISA!) will instead give us “the last three years”. Completed together with the rest of the Birmingham crowd, this paper provides a realistic view of this truly amazing landscape. LISA observations at low frequencies in the 2030s will be paired with high-frequency data from LIGO’s successors (the so-called 3rd generation detectors). Together (and that’s crucial, together!) LISA and 3g detectors will tell us the full story of the life of merging black holes. LIGO alone is like catching up with a movie because you were late at the theatre, LISA alone is like a huge cliffhanger before the series finale… multiband observations are a bingewatching experience!
Antoine Klein, Geraint Pratten, Riccardo Buscicchio, Patricia Schmidt, Christopher J. Moore, Eliot Finch, Alice Bonino, Lucy M. Thomas, Natalie Williams, Davide Gerosa, Sean McGee, Matt Nicholl and Alberto Vecchio.
arXiv:2204.03423 [gr-qc].
April 4, 2022
Daria’s new paper is out! (With key contributions from others in the group… This is also Viola’s first paper!).
Here we look at sub-dominant black-hole spin effects in current data from LIGO and Virgo (yeah sorry guys… our black-hole spin obsession goes on). People have looked at spin precession before, but we’re interested in even more subtle things, namely disentangling precession and nutation. This is a tricky business, which is made complicated by the fact that this piece of information is hidden behind other parameters that are easier to measure (say the masses of the two black holes). Our paper is an attempt to formulate and systematically exploit something we called “sequential prior conditioning” (which is: mix&match priors and posteriors in Bayesian stats…). Results are weak today but strong tomorrow.
Daria Gangardt, Davide Gerosa, Michael Kesden, Viola De Renzis, Nathan Steinle.
Physical Review D 106 (2022) 024019.
arXiv:2204.00026 [gr-qc].
March 11, 2022
LISA astrophysics is awesome and everything you might ever want to know is written this paper. [Sorry for the short blog post, but there isn’t much else to say really…] A huge thanks to all the captains that put this massive community-wide effort together.
Pau Amaro-Seoane, et al. (155 authors incl. Davide Gerosa).
arXiv:2203.06016 [gr-qc].
March 9, 2022
It took a while (so many technical challenges…) but we made it! Matt‘s monster paper is finally out!
Let me introduce a fully-fledged pipeline to study populations of gravitational-wave events with deep learning. If it sounds cool, well, it is cool (just look at the flowchart in Figure 1!). We can now perform a hierarchical Bayesian analysis on GW data but, unlike current state-of-the-art applications that rely on simple functional form, we can use populations inferred from numerical simulations. This might sound like a detail but it’s not: it’s necessary to compare GW data directly against stellar physics. While we don’t do that yet here (our simulations are admittedly too simple), there’s a ton of astrophysics already in this paper. Whether you care about neural networks or hierarchical black-hole mergers (or, why not, both!), sit tight, fasten your seatbelt, and read Matt’s paper.
Matthew Mould, Davide Gerosa, Stephen R. Taylor.
Physical Review D 106 (2022) 103013.
arXiv:2203.03651 [astro-ph.HE].
March 2, 2022
I just had the first lectures of a class I’m teaching for the first time: Astrostatistics and Machine Learning (sounds exciting? Well, it is!). This is an advanced course for the MSc degree in Astrophysics and Space Science at the University of Milano-Bicocca. My students and I will travel across data inference, Bayesian wonders, sampling, regression, classification, and become best friends with deep learning. All of this is applied to astrophysical datasets.
The entire class is available under the form of jupyter notebooks at github.com/dgerosa/astrostatistics_bicocca_2022. The repository is hooked up with the mybinder service.
February 23, 2022
Huge congrats to my student Cecilia Fabbri who got her Bachelor’s degree today. Cecilia defended (quite brilliantly!) her project titled “Constraining the black-hole irreducible mass with current gravitational-wave data”. Her work ended up in our recent draft (arxiv:2202.08848). Cecilia is continuing with a Master’s degree in astrophysics at Milano-Bicocca, stay tuned for her future successes!
February 21, 2022
Spinning black holes are weird (well, all black holes are weird but those that spin are the worse!). They have a funny thing called ergoregion where orbiting particles can have negative energy. Penrose was the first to realize that this can be exploited to extract energy from the black hole itself. The thing is, even if you figure out how to do it, you’re inevitably going to spin the black hole down. At the end of the day, you’re left with a fossil black hole that does not have any spin. The mass of that leftover black hole (“What’s for lunch dear? Fancy some sushi or prefer a black hole?”) is called irreducible mass. Hawking (another giant!) figured out this has to do with thermodynamics.
Long story short, in this paper we compute the irreducible mass of the black holes detected in gravitational waves by LIGO. It was funny to re-discover that gravitational wave detection was indeed the motivation behind Hawking original proof of the area theorem (he had Weber‘s claimed detection in mind at the time). The story behind our paper starts as a toy calculation with my undergraduate student Cecilia and ended up in a neat, hopefully informative exploitation of LIGO data. We reparametrized LIGO’s black-hole properties using the rotational and rotational contributions to their total energy, we ranked current gravitational-wave events according to their “irreversibility”, and we compute a sort of population version of the area law. Enjoy!
Davide Gerosa, Cecilia Maria Fabbri, Ulrich Sperhake.
Classical and Quantum Gravity 39 (2020) 175008.
arXiv:2202.08848 [gr-qc].
January 20, 2022
Traveling is (kind of) coming back, and we’re having lots of visitors around, all supported by external research grants (congrats folks, you’re great!)
Safe travel everyone, it’s time we move our group meetings to a larger room.
January 7, 2022
I’m very happy to share that I was awarded a 330k EUR grant from the Cariplo Foundation. Cariplo is a trust that supports scientific research in the Lombardy region of Italy. Our proposal is titled “Deep into the relativistic two-body problem“, though arguably a better title could have been “more black-hole fun coming our way”!
December 6, 2021
My group and I are now part of TEONGRAV, which is the Italian national initiative dedicated to gravitational theory and phenomenology. TEONGRAV is run by the INFN (National Institute for Nuclear Physics) and, besides the other folks here in Milan, it counts members from Florence, Rome, Naples, Padua, Trento, and Trieste. Looking forward to new exciting collaborations, all surrounded by good Italian coffee of course!
November 17, 2021
Breaking things is fun! In the previous paper of this series, we looked at accretion disks around massive black-hole binaries and found things were going awry. We kept on finding configurations that our implementation could not handle… And now we know this is real! Finding disk solutions when the spin of the black hole has a large misalignment is just not possible! And that’s because the disk really breaks into different sections. We’ve now checked it with state-of-the-art hydrodynamical numerical simulations that not only confirm what we suspected but also show some funny things (like breaking being prevented by disk spirals, etc). I was serious, breaking things is real fun!
Check out Rebecca’s beautiful movies!
Rebecca Nealon, Enrico Ragusa, Davide Gerosa, Giovanni Rosotti, Riccardo Barbieri.
Monthly Notices of the Royal Astronomical Society 509 (2022) 5608–5621.
arXiv:2111.08065 [astro-ph.HE].
October 13, 2021
Great Scott, a new paper! When analyzing gravitational-wave data, looking at one black hole at a time is not enough anymore, the fun part is looking at them all together. The issue Matt and I are tackling here is that one needs to be consistent with putting together different events when fitting the entire population. This is obvious for things that do not change (say the masses of the black holes, those are what they are), but becomes a very tricky business for varying quantities (say the spin directions, which is what we look at here). In that case, it’s dangerous to put together events taken at different stages of their evolution. And the solution to this problem is…. time travel! We show that but propagating binaries backward in time, one can put all sources on the same footing. After that, estimating the impact of the detector requires traveling forward in time, so going “back to the future”. After all, we all know that post-Newtonian black-hole binary integrations look like this:
Matthew Mould, Davide Gerosa.
Physical Review D 105 (2022) 024076.
arXiv:2110.05507 [astro-ph.HE].
October 11, 2021
Nathan Steinle is officially starting his postdoc in the group today! Nate graduated with Mike Kesden at the University of Texas at Dallas and is now working with me and the rest of the Birmingham crowd. Welcome Nate! Hope you enjoy this side of the pond.
October 4, 2021
The University of Milan-Bicocca (Italy) invites expressions of interest for postdoctoral positions in gravitational-wave astronomy.
Successful candidates will join Prof. Davide Gerosa and will constitute the core team of the “GWmining” project funded by the European Research Council. Targeted investigations include applications of machine-learning techniques to gravitational-wave physics, modeling of black-hole binary populations from their stellar progenitors, relativistic dynamics, and statistical inference. Candidates will have ample opportunities to explore other areas of gravitational-wave astronomy and will be encouraged to develop independent collaborations.
We anticipate awarding two positions. Appointments will be for a three-year term and come with generous research and travel budget. The starting date is negotiable.
The astrophysics group at Milan-Bicocca provides a vibrant environment with expertise covering all aspects of gravitational-wave astronomy, relativistic astrophysics, and numerical relativity, as well as a wider astronomical context including observational and experimental activities. The group has tight connections with the LISA Consortium, the Virgo Collaboration, and the Italian National Institute for Nuclear Physics (INFN) via the TEONGRAV national initiative. Faculty members with matching interests include Gerosa, Sesana, Colpi, Giacomazzo, and Dotti.
Milan is a beautiful, international city in the north of Italy. Mountains and lakes are just around the corner.
Successful candidates will have a PhD in Physics or related discipline, strong programming skills, and previous experience in one or more of the following topics: gravitational-wave astronomy, stellar evolution, relativistic astrophysics, general relativity, machine learning, statistical inference.
Applications should include a CV with a list of publications and a two-page statement covering research interests and plans. These should be sent to [email protected] by December 1st, 2021 for full consideration. Candidates should also arrange for at least two, but preferably three, reference letters to be sent to the same address by December 1st, 2021. We strive to build a diverse and inclusive environment and welcome expressions of interest from traditionally underrepresented groups.
For inquiries please do not hesitate to contact Davide Gerosa at [email protected].
September 18, 2021
Viola De Renzis is the latest addition to our group! Viola graduated from Rome “La Sapienza” with an MSc thesis on exotic compact objects and is now starting her PhD with me at Milan-Bicocca. Viola plays guitar, arguably better than Matt (although he runs for a million miles, and that’s when he’s tired), while Daria remains by far the best fencer in the group. Welcome, we all look forward to working with you!
September 8, 2021
It is a true honor to receive the career Prize for Young Researchers of the Italian Society for General Relativity and Gravitational Physics (SIGRAV). I was awarded the prize in the class of relativistic astrophysics. It’s amazing to be recognized in my home country; it’s great to be back! Let me thank all my mentors, advisors, collaborators, and now students who are walking with me in the adventure of science.
Here is me with the president of the society Fulvio Ricci. And here are press releases from the University of Milan-Bicocca and the INFN.
September 1, 2021
We moved! I’ve had the opportunity to relocate to Milan, in the north of Italy, very close to where I’m from. I’m now an Associate Professor at the University of Milan-Bicocca, one of the two campuses in the beautiful city of the “Madonnina“. Some of the folks in my group will be visiting Milan very often, and (spoiler alert!) we’re going to have new additions soon. I’m sad to leave the amazing group in Birmingham, but also very excited at this new tremendous opportunity.
August 6, 2021
No black hole is an island entire of itself.
We’ve got many gravitational wave events now. One can look at each of them individually (aka “parameter estimation”), all of them together (aka “population”), or each of them individually while they’re together. That’s what we do in this paper: we look at the properties of individual gravitational-wave events in light of the rest of the observed population. The nice thing is that all of these different ways of looking at the data are part of the same statistical tool, which is a hierarchical Bayesian scheme. Careful, heavy stats inside, don’t do this at home.
Christopher J. Moore, Davide Gerosa.
Physical Review D 104 (2021) 083008.
arXiv:2108.02462 [gr-qc].
July 14, 2021
Huge congrats to Maciej (Max) Dabrowny, who just graduated from the University of Birmingham after a very successful research project with us (Max’s project ended up in a paper!). Well done and all the best for the future.
July 11, 2021
I was recently interviewed for the Italian Week of Astronomy (“Settimana dell’Astronomia”), a science festival organized by Fondazione Lombardia per l’Ambiente and supported by various Italian associations, universities, and research centers. Here is the nice clip they put together (I mean, I’m terrible at speaking to a camera, but they assembled it very well!).