Davide Gerosa

Caltech


High-accuracy mass, spin, and recoil predictions of generic black-hole merger remnants

Vijay Varma, Davide Gerosa, François Hébert, Leo C. Stein, Hao Zhang.
arXiv:1809.09125 [gr-qc].

Black hole mergers are like a scattering problem. Two black holes come in, and one black hole comes out. The difference is a bunch of gravitational waves. Those are nice, of course, but the remnant black hole is important too! Here we provide accurate predictions of the mass, spin and kick of this remnant given the properties of the two merging black holes. If you need those numbers (want to build a waveform family? or test GR perhaps?) just use our python module surfinBH!

ps. Bonus note. What if you collide ducks instead of black holes? ducks


Frequency-domain waveform approximants capturing Doppler shifts

Katie Chamberlain, Christopher J. Moore, Davide Gerosa, Nicolas Yunes.
arXiv:1809.04799 [gr-qc].

We all know Doppler shifts, right? That’s like the biibouuubiiiiboouuuuuu of an ambulance. That happens to gravitational waves as well. Suppose you have a merging binary which is emitting gravitational waves (bibooou). If that binary is going somewhere (say it’s falling into the gravitational potential of a third body), much like the ambulance, the emitted signal will be Doppler shifted. This paper shows a very nice calculation to incorporate Doppler shifts into gravitational waves.

ps. This started out as Katie’s undergraduate summer project at Caltech. Congrats Katie!


Giulio Rampa thesis prize

I was recently awarded the 2018 Giulio Rampa Thesis Prize for Outstanding Research in General Relativity. The prize is sponsored by the University of Pavia (Italy) and the Italian Society for Relativity and Gravitational Physics (SIGRAV), and was officially awarded at the 23rd SIGRAV Conference. The prize announcement reads:

Dr. Gerosa’s Ph.D. Thesis on “Source modelling at the dawn of gravitational-wave astronomy” shows an impressive ability to master a rather broad range of topics in relativistic astrophysics and gravitational wave physics. The research initiated by Dr. Gerosa in these areas has triggered follow-up work, providing new important insights and new physical scenarios. The large impact that the work of Dr. Gerosa has already had can only continue to grow.


Spin orientations of merging black holes formed from the evolution of stellar binaries

Davide Gerosa, Emanuele Berti, Richard O’Shaughnessy, Krzysztof Belczynski, Michael Kesden, Daniel Wysocki, Wojciech Gladysz.
Physical Review D 98 (2018) 084036.
arXiv:1808.02491 [astro-ph.HE].
Supporting material available here.

Today’s paper celebrates the wedding of startrack and precession (the nickname for this project was pretrack 😉 ). We use population synthesis evolution from startrack to predict the parameters of spinning black-hole binaries observed by LIGO. The spin distribution is then propagated from formation to detection using post-Newtonian evolutions from my precession code. The bottom line is that spin measurements can be used to truly reconstruct the binary formation channels, and some specific mechanisms (like mass transfers, tides, natal kicks, supernova’s instabilities etc.). Our database is publicly available (play with it!), as well as a little code to compute gravitational-wave detectabilities.

Supporting material available here.

Update: this is my 25th published paper! That’s silver, right?


Optimizing LIGO with LISA forewarnings to improve black-hole spectroscopy

Rhondale Tso, Davide Gerosa, Yanbei Chen.
arXiv:1807.00075 [gr-qc].

LISA is going to be amazing: supermassive black-holes, galactic white dwarfs, EMRIs… Besides all of that, LISA can help us doing LIGO’s science better. Some LIGO’s sources (notably, things like GW150914) will show up in LISA years is advance. LISA is going to tell us when (in time) and where (in frequency) LIGO will see these sources. In this paper, we explore the idea of adapting the LIGO noise curve if one knows that a source is coming in (because LISA told us). We apply this idea to ringdown tests of GR, and show how powerful they become!

Other press coverage: astrobites.


Mining gravitational-wave catalogs to understand binary stellar evolution: a new hierarchical bayesian framework.

Stephen R. Taylor, Davide Gerosa.
Physical Review D 98 (2018) 083017.
arXiv:1806.08365 [astro-ph.HE].

Gravitational-wave astronomy is moving. Quickly. In a few years we are going to have large catalogs of many detections, and a whole lot of information to extract from them. Instead of focussing on parameters (masses, spins, redshifts) of single sources, we will want to extract hyperparameters describing physical features of the population (metallicity, natal kicks, common envelope, stellar winds, etc). Here we show how to do this in practice: read our new paper for an amazing journey through hyperlateral cubes, Gaussian process emulators, selection biases, hierarchical modeling and more.

Our tools are publicly available! Here is Steve’s Webpage and our public code.


Numerical Relativity beyond General Relativity

Happy to report about the great success of our workshop ”Numerical Relativity beyond General Relativity”. This was organized by me, Helvi Witek and Leo Stein at the Benasque physics center (Spain), in the beautiful region of the Pyrenees, on June 3-9, 2018. Was great to see world-leading experts from so many different fields (numerical relativity, gravitational-wave data analysis, self-force, theoretical physics, cosmology, etc) interacting and reporting their progress on innovative uses of computational techniques in gravitation. Here are the conference program and (some of) the talk’s slides.

I only wish the rain would have stopped for more than a few hours over the entire week. This is us with Einstein; we’re all beyond!

nulrelconf.jpg