Davide Gerosa

November 22, 2023



Calibrating signal-to-noise ratio detection thresholds using gravitational-wave catalogs

In the gravitational-wave world, we usually say a binary merger is detected if it has a sufficiently large SNR (signal-to-noise ratio). But is that true? Detection pipelines are far more complicated than that. Here we try to figure out a section threshold from what’s detected. That is: (some) people agree that these guys are GWs, so what’s your SNR threshold for detectability? It’s like reading in the minds of a GW data analyst…

Matthew Mould, Christopher J. Moore, Davide Gerosa.
arXiv:2311.12117 [gr-qc].

November 21, 2023



Starting a new class! “Scientific computing” for PhD students

I’m teaching the first lecture of a new class today. This is “Scientific computing with Python,” a 16h module for PhD students. To the (many) PhD students who signed up: thanks for your interest, hope you’ll like this. BTW the title says Python but there will also be some Mathematica and some git, just for fun. My material is online at

github.com/dgerosa/scientificcomputing_bicocca_2023

Have a look if you want and please do give feedback if you do 🙂

November 20, 2023



November graduations: 4 Bsc projects with us

We had another graduation session in November, and a whopping 4 people graduated with research projects in our group. Here are the new BSc physicists who just defended:

  • Matteo Falcone worked with the other Matteo (Boschini) on a simulation design strategy for machine learning;
  • Serena Caslini worked with Nick on a new strategy to classify burst GW signals;
  • Marco “104” Bianchi worked with Giulia and put together a neural network for black-hole binary spin precession using his gaming GPU 🙂
  • Martin “Top” Gerini was supervised by Alice on supermassive black holes, LISA, and glitches.

Congrats all (and twice congrats to Marco and Serena, who graduated with full marks and honors). It was great working with you. Matteo and Martin are now enrolled in an MSc degree in Artificial Intelligence (good luck!), while Marco and Serena are starting our MSc degree in Astrophysics.

October 31, 2023



Spin-eccentricity interplay in merging binary black holes

I’m obsessed with spinning black-hole binaries but, guys, spinning and eccentric black holes are even better! This is the first first-author paper by Giulia, who is not only a rising GW astronomer but also a semi-professional baker… So take two spoons of black holes, one spoon of spin dynamics, some eccentricity (but less than 0.6 ounces), and a pinch of maths. Put this in a bowl, mix it thoroughly with numerical integrations …and the result is very tasty! Spins and eccentricity shape the dynamics of black-hole binaries together, which means one can hope to measure eccentricity indirectly from the spins, but also that if you forget about eccentricity then your spin inference will be crap. Buon appetito.

Giulia Fumagalli, Davide Gerosa.
arXiv:2310.16893 [gr-qc].

October 28, 2023



2 Masters + 2 Undegrads

We’ve had four amazing research students graduating with us in October!

  • Alessandro Santini defended his MSc project, which was actually completed in part at Johns Hopkins University (USA) with R. Cotesta and E. Berti. Alessandro worked our a possible astrophysical model to explain the mass-spin correlation observed by LIGO. We’ve published this already! Alessandro is moving on with a PhD at the AEI in Potsdam, Germany.
  • Francesco Nobili also got his MSc degree. His project was completed with S. Baghwat at the University of Birmingham as is about fitting ringdown amplitudes. I discovered other students call him “Brock” from the Pokemon character, so I started doing the same… Brock is starting a PhD in computational astrophysics at the University of Insubria in Como, Italy.
  • Federico Ravelli. Completed a shorter BSc project with Viola De Renzis on spin effects in LIGO/Virgo data…
  • … and Simone Sferlazzo also got his Physics BSc degree. Simone worked with Michele Mancarella on “the use and abuse” (cit.) of Fisher matrices in GWs.

After the Master’s defenses, students turned the graduation party into a football supporter thing, with chants and all the rest!

October 14, 2023



Arianna on a national newspaper

Arianna Renzini (Marie Curie Fellow in my group) is on the Italian national newspaper “Corriere della Sera” today!

Here is the online version: Arianna Renzini, la studiosa di Astrofisica corteggiata da tutto il mondo: «Basta cervelli in fuga, lavorerĂČ a Milano»

But it was also on the printed thing distributed everywhere!

(That picture was taken in my office… So my office is also in the national newspaper today! Wooo!)

October 11, 2023



The cosmic variance of testing general relativity with gravitational-wave catalogs

…and we’re back to testing GR. We’ve got many gravitational-wave events and would like to use them all together to figure out if our equations for gravity are correct. And here is the issue: there’s only one set (aka catalog) of black holes that contains all the black holes we’ve observed. Now that’s obvious you’d say, and you would be right!, much like we have a single Universe to observe (I’m not a language guy but indeed “Universe” means like “the whole thing”). This effect is known in cosmology (think those low-order multiples in the usual CMB plot), so we called it “the cosmic variance of testing GR”. It’s bad, but the Baron Munchauseen tells us we can bootstrap.

Costantino Pacilio, Davide Gerosa, Swetha Bhagwat.
arXiv:2310.03811 [gr-qc].

October 6, 2023



More people, more topics, more fun

Our group is getting some tremendous additions, with 5 people joining in the fall of 2023! The scope of our research is getting broader and broader 🙂

  • Pippa Cole is joining us as a postdoc from Amsterdam and she’s going to teach us fun things about dark matter, environmental effects on GW measurements, primordial black-holes etc.
  • Ssohrab Borhanian is also coming in as a postdoc (from Jena, Germany and Penn State before that), with all you can ever hope to know about 3G detectors.
  • Nick Loutrel is a new postdoc from Rome (and Princeton before, and Montana before) which strengthens the analytical / modeling side of the group.
  • Arianna Renzini is coming as a postdoc from sunny Caltech with her own Marie Curie Fellowship, ready to make a splash with stochastic gravitational-wave backgrounds!
  • Matteo Boschini is a new PhD student, after a successful MSc degree with a cool project on numerical-relativity surrogate models.

We’re soon going to have Giulia Capurri who will be visiting us for a few months from Trieste. Welcome aboard all! There are like 13 people at group meetings now…

September 20, 2023



Students going for 3G, ringdowns, and selection effects

Three of our BSc students graduated today.

  • Ludovica Carbone worked with Michele Mancarella and Francesco Iacovellie and has some nice forecasts for 3G detectors.
  • Riccardo Bosoni de Martini was supervised by Costantino Pacilio and checked super carefully their Fisher code for ringdowns.
  • Malvina Bellotti (who, I’m very envious, is from Cortina in the mountains!) worked with me on selection effects for GW surveys.

And, last but not least, let me add Simone Piscitelli, who last week defended his MSc degree at Milano Statale (“the other” University of Milan) supervised by Costantino Pacilio and myself. Simone worked on a cool test of GR. Stay tuned…

Congrats all!

September 17, 2023



Postdoc positions in gravitational-wave astronomy at Milano-Bicocca (Italy)

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, with additional support from national grants. 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, as well as applications of statistical and machine-learning tools to gravity (although we are open to all candidates with a strong gravitational-wave and/or high-energy astrophysics background!). Candidates will have ample opportunities to kickstart new projects with group members and will be strongly encouraged to develop their own independent research lines.

We anticipate awarding up to three positions. Appointments will be for 2+1 years and come with a generous research and travel budget. The starting date is negotiable.

The astrophysics unit 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 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 15th, 2023 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 15th, 2023.

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]

August 28, 2023



Black-hole mergers in disk-like environments could explain the observed 𝑞−𝜒eff correlation

Gravitational-wave data keep on giving us surprises. The most outstanding one IMO is an observed correlation between mass ratios and spins of the black holes, which was first found by Tom Callister and friends. That is so, so weird… to the point that virtually zero astrophysical models so far can explain it fully and consistently. Well, we can’t either (at least not fully and consistently) but we think this paper is a nice attempt. The secret seems to be the symmetry of the astrophysical environment one considers, and data tends to prefer black holes assembled in cylindrical symmetry. That’s also weird to be honest, but there’s a candidate for this setup, namely accretion disks and their migration traps. Who knows, more data will tell.

… and huge congrats to my MSc student Alessandro who managed to publish a paper even before graduating!

Alessandro Santini, Davide Gerosa, Roberto Cotesta, Emanuele Berti
arXiv:2308.12998 [astro-ph.HE].

July 19, 2023



New July physicists

Two students just completed their Bachelor’s degree with research projects in our group. Leonardo Toti worked with myself and Giulia Fumagalli on exploring black-hole merger trees in dense clusters, while Simone Restuccia worked with Costantino Pacilio on applying dimensionality-reduction techniques to black-hole ringdowns. I had the honor of heading their graduation committee and could call them “physicists” for the very first time (and the Italian ceremonial phase is imposing: “coi poteri conferitami…“). Congrats Simone and Leonardo!

July 17, 2023



gwpopnext was a blast!

Last week my group and I hosted the international workshop “Gravitational-wave populations: what’s next?.” It’s been a blast!

An unconventional conference, with almost zero talks and the vast majority of the time dedicated to discussions. I report the program here below, just to give you a feeling of what we discussed. The conference started with the question “How many of you entered the field after GW150914?” and virtually everyone raised their hand! It was so refreshing to see our field is alive.

We then went through population synthesis simulations, fancy statistical methods (I promise I’ll understand nonparametric methods one day!), intricacies of injections, catalogs, and overlap with our EM observer friends. We took a break on Wednesday for a social activity on Lake Como, with some folks diving into the lake and others hiking up to a small castle. All before dinner with a fascinating lake (and thunderstorm!) view.

Thanks all for joining and participating so actively. Huge thanks to Emanuele Berti and Salvo Vitale for co-organizing this with me, as well as the local GW group for assistance. Finally, congrats to Amanda Farah and Alex Criswell who won our SIGRAV early career prize.

And if you couldn’t make it for whatever reason no worries, we’ll do it again!

Conference program in a nutshell. These are our discussion sessions

  • Intro: the pieces of the population problem.
  • What can/should astrophysicists and pop-synthers predict?
  • What is the predictive power of pop-synth codes? Are we learning more than our assumptions?
  • Hierarchical Bayesian fits: can we keep on doing this? Technical difficulties, scaling with the number of events, selection effects.
  • Mind the outliers. Are they in or out of your fit? If you fit something well you also need to fit the rest.
  • What is a catalog? Is p_astro the way to go? (Ir)relevance of subthreshold events.
  • Mind the systematics. Are waveform/calibration impacting the population? And how about the assumed population?
  • Beyond functional forms: “non-parametric” methods. What are they and what does it even mean.
  • Beyond functional forms: “parametric but informed”. Machine learning emulators for pop-synth.
  • More populations. LISA, X-ray binaries, Gaia, you name it.
  • More than individual mergers. Stochastic backgrounds, foreground removal.
  • Adding the redshift dimension: toward 3g! Use the population to do cosmology.
  • What’s next? Summary and prospects.

July 10, 2023



Extending black-hole remnant surrogate models to extreme mass ratios

New paper from a new student! Here is Matteo Boschini’s first piece of work, where we look at predictions for the final mass and spins of black-hole remnants. That is, after two black hole merge, what’s the mass and spin of the guy they left behind? These predictions are typically done by fitting (in various ways) outputs from numerical-relativity simulations but those, unfortunately, can only handle black holes of similar masses. On the other hand, black holes with masses that are very different from each other can be handled analytically. Here we show how to put the two together with a single machine-learning fit.

Matteo Boschini, Davide Gerosa, Vijay Varma, Cristobal Armaza, Michael Boyle, Marceline S. Bonilla, Andrea Ceja, Yitian Chen, Nils Deppe, Matthew Giesler, Lawrence E. Kidder, Guillermo Lara, Oliver Long, Sizheng Ma, Keefe Mitman, Peter James Nee, Harald P. Pfeiffer, Antoni Ramos-Buades, Mark A. Scheel, Nils L. Vu, and Jooheon Yoo.
arXiv:2307.03435 [gr-qc].

June 21, 2023



Phd position at Milano-Bicocca under the Italian National PhD program in Space Science and Technology

The University of Milano-Bicocca (Milan, Italy) will be hiring a PhD student under the Italian National PhD program in Space Science and Technology. Candidates with interests in gravitational-wave astronomy, data analysis, and multi-messenger applications are encouraged to apply. For information please see:

The application deadline is July 6th, 2023 at 4pm CEST. For informal enquiries please contact Monica Colpi ([email protected]).

June 19, 2023



Masterclass in big data within science and industry

The advanced class “Big data within science and industry” will take place on September 22nd at the University of Milano-Bicocca (Milan, Italy).

https://sites.google.com/unimib.it/bigdatamasterclass

Data are everywhere. Exploring scientific data is now at the heart of both scientific advances as well as industrial applications. This one-day master class provides a “learn by example” introduction to the fascinating world of big data, namely pieces of information that are so rich and structured that require targeted analysis techniques loosely referred to as machine learning or artificial intelligence.


The class is suitable for advanced MSc students, PhD students, and postdocs who wish to expand their proficiency in handling scientific data. The program features the participation of three world-leading experts from both academia and the private sector, as well as a hands-on experience for all participants.

For students enrolled in the Physics and Astronomy PhD program here at Milano-Bicocca, this 8-hour program will be recognized with 1 CFU. In any case, we are happy to provide attendance certificates.

Interested students should register by September 8th, 2023. Participation is free of charge. We hope to accommodate everyone, but depending on the number of people registering, participants might need to be selected.

Davide Gerosa, Michele Fumagalli (Milano-Bicocca)

June 8, 2023



Dr. Matt!

Please let me introduce Dr Matthew Mould… After N papers (where N is a lot) and a 4h+15min viva discussion, Matt has completed his PhD in gravitational-wave astronomy at the University of Birmingham. WooooO! The examiners were Annelies Mortier from Birmingham and Uli Sperhake from Cambridge, who went through a thesis with more than 600 references…. Matt will be continuing his already successful career with a postdoc at MIT, LIGO lab. From my side, Matt is (actually, was!) my first PhD student and spending 3+ years working with him has been amazing. Thanks, Matt for teaching me Bayesian stats and never letting go when I was saying crap.

First thing you do after a 4h 15m viva? Eat a carefully baked cookie by Giulia!

June 7, 2023



Glitch systematics on the observation of massive black-hole binaries with LISA

All right, this is kind of far from my day-to-day topics but working on this paper with Alice and Riccardo was super fun. Think LISA and supermassive binary black holes. And… the detector does what it wants. That’s not true of course because the experimentalists are amazing, but there will be noise transients: unexpected blips when the gravitational-wave signal will be corrupted. Here we look at what would happen in a realistic setting when a LISA glitch happens on top of a gravitational wave from a supermassive black hole.

Alice Spadaro, Riccardo Buscicchio, Daniele Vetrugno, Antoine Klein, Davide Gerosa, Stefano Vitale, Rita Dolesi, William Joseph Weber, Monica Colpi.
arXiv:2306.03923 [gr-qc].

June 6, 2023



Let’s PRIN!

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!).

June 3, 2023



IREU summer time

Welcome Harrison Blake! My group is hosting a student from the IREU program in Gravitational Physics, which is administered by the University of Florida. Harrison is visiting from Ohio State University and will be working with Michele Mancarella on forecasting the science with can do with gravitational waves from the Moon…

May 30, 2023



One to many: comparing single gravitational-wave events to astrophysical populations

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



QLUSTER: quick clusters of merging binary black holes

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



Parameter estimation of binary black holes in the endpoint of the up-down instability

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.
Physical Review D 108 (2023) 024024.
arXiv:2304.13063 [gr-qc].

April 12, 2023



Efficient multi-timescale dynamics of precessing black-hole binaries 

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.
Physical Review D 108 (2023) 024042.
arXiv:2304.04801 [gr-qc].
Open-source code: homepage, repository, documentation.

March 29, 2023



Inferring, not just detecting: metrics for high-redshift sources observed with third-generation gravitational-wave detectors

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.
Physical Review D Letters 107 (2023) L101302.
arXiv:2303.16323 [gr-qc].

March 23, 2023



PhD positions in gravitational-wave astronomy at Milano-Bicocca

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:

https://en.unimib.it/education/postgraduates/doctoral-research-phd-programmes/applying-doctorate/calls-application

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



Spring graduations!

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!

That’s Matteo discussing black-hole remnants…

February 27, 2023



We should learn from our students: LISA and beyond

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



Gravitational-wave populations: what’s next?

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



New year, new friend

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



Two more graduations today!

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



Eccentricity or spin precession? Distinguishing subdominant effects in gravitational-wave data

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



The Bardeen-Petterson effect, disk breaking, and the spin orientations of supermassive black-hole binaries

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



Here are the new gravitational wave astronomers!

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).

Here we are, from left to right: Alessandro (sorry I cut your face in half!), me trying to be funny, Riccardo, and smiling Alice! (Lorenzo and Viola had left the room earlier…)

October 13, 2022



Late 2022 visitors: we’re alive!

My group is hosting quite a few visitors this semester. We’re alive!

  • Francesco Iacovelli is visiting us for 7 (!) months from Geneva with a grant from the Istituto Svizzero. Francesco has done some amazing work on forecasting the capabilities of Einstein Telescope.
  • Chris Moore, a longstanding collaborator from the University of Birmingham will be here at the end of October
  • Clement Bonnerot (now in Copenhagen but about to move to the UK for a faculty job, congrats!) will join us in late November.
  • Swetha Baghwat will be visiting Milan from Birmingham in November as well.
  • And Lieke van Son, Phd student at Harvard and population-synthesis mastermind, will be here in early December.
Left to right: Giulia, Viola, Michele, Lieke, Costantino, Francesco, Alice, and me

October 12, 2022



The group gets larger

So many new people are joining us this Fall!

  • Michele Mancarella is joining us as a postdoc supported by my ERC grant. He’s moving from Geneva (Switzerland) brings with him some new activities on gravitational-wave cosmology, because astronomy was not enough after all 🙂
  • Costantino Pacilio is also coming in as a postdoc on my ERC grant. Costantino is a GR tester and is providing the group with some new connections to fundamental physics.
  • Giulia Fumagalli is about to start her PhD with us, also supported by the ERC. She’s already done some amazing work with Alberto Sesana and Golam Shaifullah on pulsar timing array. Now ready for new GW adventures!
  • And spoiler alert! There’s another PhD student joining in a few months
 More soon!

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



Postdoctoral fellowships in gravitational-wave astronomy at Milano-Bicocca (Italy)

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



Andrea and Oliver are the new black-hole experts in town!

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!

Here is me (center, the guy who still needs to learn how to take a selfie), Riccardo (far right), the star of the day Andrea (front right) together with Alberto (green guy) and his student Serena (left) who also brillantly defended her astrophysics MSc thesis today.

September 19, 2022



Job opportunities for Marie Curie past holders and applicants

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

https://www.unimib.it/ricerca/opportunita/finanziamenti-alla-ricerca/finanziamenti-nazionali/bando-giovani-ricercatori-vincitori-msca-young-researchers-msca-grants-winners

(ii) Seal of Excellence holders:

https://www.unimib.it/ricerca/opportunita/finanziamenti-alla-ricerca/finanziamenti-nazionali/bando-giovani-ricercatori-seal-excellence-msca-call-young-researchers-seal-excellence-msca

August 30, 2022



Italy has a brand new Center for Supercomputing (ICSC)… and we’re on it!

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



Characterization of merging black holes with two precessing spins

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 3, 2022



Super Arianna!

Very happy to report that Arianna Renzini (currently a postdoc at Caltech) was awarded a prestigious Marie SkƂodowska-Curie Fellowship from the European Union, to be hosted here with my group. Arianna will bring expertise in modeling the gravitational-wave stochastic background, which is a key target for both current and future experiments. Arianna’s proposal is titled “Stochastic rewind and fast-forward: calibrating LISA with LIGO’s black holes and stochastic background.” Huge congrats, can’t wait to welcome you here.

June 1, 2022



New summer means new summer projects

We’re having four (!) summer students joining the group this year!

  • Diego Padilla Monroy from Florida International University (Miami) will be working with me in Milan supported by the IREU program.
  • Derin Sivrioglu from Grinnell College (Iowa) will be working with Daria Gangartd in Milan.
  • Sayan Neogi from the Indian Institute of Science, Education and Research (Pune, India) will be working with Matt Mould in Birmingham.
  • Sarah Al Humaikani from Paris (France) will be working with Nathan Steinle in Birmingham.

Welcome all! We look forward to seeing your summer discoveries!

May 25, 2022



Which black hole formed first? Mass-ratio reversal in massive binary stars from gravitational-wave data

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].

April 26, 2022



PhD in gravitational physics!

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:

https://en.unimib.it/education/postgraduates/doctoral-research-phd-programmes/applying-doctorate/calls-application

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:

  • “Gravitational-wave data and black-hole binary dynamics”, supervised by Gerosa. Possible research directions include statistical inference from LIGO/Virgo and LISA data, application of machine-learning tools to gravitational-wave astronomy, and theoretical investigations of black-hole binaries.
  • “Dynamics of massive black hole binaries in dense stellar systems”, supervised by Sesana and Gualandris. This is a dual-doctorate position in partnership with the University of Surrey, UK. The main focus is the understanding of binary evolution using N-body simulations and analytical modeling. The successful candidate will spend 50% of their time at Bicocca and 50% of their time at Surrey.

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



Long-term research appointment in computational astrophysics at Milano-Bicocca (Italy)

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]).