Davide Gerosa

Caltech


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].

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.

Editor’s coverage in APS’s Kaleidoscope.


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!

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Gravitational-wave astrophysics with effective-spin measurements: asymmetries and selection biases

Ken K. Y. Ng, Salvatore Vitale, Aaron Zimmerman, Katerina Chatziioannou, Davide Gerosa, Carl-Johan Haster.
Physical Review D 98 (2018) 083007.
arXiv:1805.03046 [gr-qc].

LIGO can measure spins. Well, effective spins actually. These are special combinations of the two spins (magnitude and direction) and the binary mass ratio. There’s a ton of astrophysics that can be done just with this quantity, but one should always be careful. Today’s paper points out a few important shortcomings when dealing with effective spin measurements. Want to know more about asymmetries and selection biases?

ps. You can hardly find a better day to post a paper on the arxiv than May 4th


34th Pacific Coast Gravity Meeting

The 34th edition of the Pacific Coast Gravity Meeting, sponsored by the APS, was held at Caltech on March 16-17, 2018. This’ year edition was organized by me, Leo Stein and a few others, and was dedicated to Jim Isenberg who first started the Pacific Gravity meetings 34 years ago. We had a beautiful blend of people (including some very talented undergrads!) and topics (from numerical relativity, to quantum gravity, high-energy physics and gravitational-wave astronomy). I hope everybody had fun. I surely did!

Here is the conference program, and this below is the logo that I designed (It’s supposed to be Newton’s apple with some gravitational waves in Caltech’s orange color; I know, I’m a scientist, not an artist…). And congrats to Maria Okounkova who won the best student talk award of the APS.

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