Davide Gerosa

University of Birmingham

On the equal-mass limit of precessing black-hole binaries

Equal-mass binaries correspond to a discontinuous limit in the spin precession equations. A new constant of motion pops up, which can be exploited to study the dynamics. This is a really neat calculation done with Jakub, a Cambridge undergraduate student. Also, my first paper at Caltech!

Davide Gerosa, Ulrich Sperhake, Jakub Vošmera.
Classical and Quantum Gravity 34 (2017) 6 ,064004.
arXiv:1612.05263 [gr-qc].

Black-hole kicks as new gravitational-wave observables

Black hole kicks are cool: powerful (up to thousands of km/s!) recoils that black holes receive following a merger. Here we show these events might leave an imprint on the emitted gravitational waves, which is potentially detectable by future interferometers.

Davide Gerosa, Christopher J. Moore.
Physical Review Letters 117 (2016) 011101.
arXiv:1606.04226 [gr-qc].
Selected as PRL Editors’ Suggestion.
Press releases: Cambridge UniversityCambridge Center for Theoretical Cosmology
Other press coverage: Daily Mailphys.org, Particle Bitesegno.gr (Greek), Daily Galaxy, RegisterMedia INAF (Italian), IneffableIsland, AstronomyNow, Accademia delle Stelle (Italian), noticiasdelaciencia (Portuguese). Blog posts on astrobites and particlebites. TV interview, aired on Cambridge TV.

PRECESSION: Dynamics of spinning black-hole binaries with python

Here we present my numerical code precession, which implements our multi-timescale way to look at spinning black-hole binaries. The paper has a detailed description of the various functions as well as lots of examples.

Update: typos in Eq. (36-37) have been fixed in v3 on the arXiv.

Davide Gerosa, Michael Kesden.
Physical Review D 93 (2016) 124066.
arXiv:1605.01067 [astro-ph.HE].
Open-source code: homepage, repository, documentation.

Numerical simulations of stellar collapse in scalar-tensor theories of gravity

Here we present 1+1 numerical-relativity simulation of stellar collapse in scalar-tensor theories, where gravity is mediated by the usual metric coupled to an additional scalar field. Bottom line: you can test General Relativity with supernovae explosions!

Davide Gerosa, Ulrich Sperhake, Christian D. Ott.
Classical and Quantum Gravity 33 (2016) 13 , 135002.
arXiv:1602.06952 [gr-qc].
Supporting material available here.

Distinguishing black-hole spin-orbit resonances by their gravitational wave signatures. II: Full parameter estimation

This is a follow up of arXiv:1403.7147, just done better. Instead of overlaps, we do real injections in LIGO parameter-estimation codes to show that spin-orbit resonances are indeed detectable.

Daniele Trifirò, Richard O’Shaughnessy, Davide Gerosa, Emanuele Berti, Michael Kesden, Tyson Littenberg, Ulrich Sperhake.
Physical Review D 93 (2016) 044071.
arXiv:1507.05587 [gr-qc].

The birth of an idea

I wrote a post for The Birth of an Idea, which is a really beautiful blog collecting insights on how scientists start their science. Thanks Vitor for the opportunity to contribute! Here is my post:

Bikes and Colorful Pieces

An idea, a good one at least, is like a gift. It’s something which is not yours (indeed, you didn’t have it before!) but comes to you, it’s given to you.

I bike to work, it’s kind of ten minutes from my place to the Cambridge Maths department, but those ten minutes can be more productive than ten hours or ten days in front of my computer’s screen. It’s morning, your mind should be clear (you should pay attention to cars while biking!), but it’s actually already getting full of what you have to do today. You get to the office, sit down, turn your computer on, and start looking at your problem. You write the equations down, try putting them in a computer, it doesn’t work, just nans coming out. You ask a collaborator who hopefully knows something, write the equations down again, it doesn’t work. You check in a paper if someone else did something similar, take a break, get annoyed (and here I typically open football websites…). Oh, and you write the same equations down again, it simply doesn’t work.

At some stage, it’s time to go home, and that moment is precious to me. You know your problem so well, those equations, that crashing piece of code, but you were looking too close. When I close my laptop and get on my way home, fresh air on my face, I can look at the problem from afar. It’s like looking at those beautiful ancient mosaics. If you look very close, you only see one colored piece, but you can’t see any meaning in it. Each piece is crucial to the final piece of art, but the value of each piece is its relation to the bigger picture. You can only appreciate a mosaic if you take one step back and look to the whole picture from afar. Wow. Biking home is my step back. You’ve been looking at all pieces for days, weeks, you know the color of each piece so well that you can finally grasp the relation which puts them together.

An idea, a good one at least, is like a gift you can say thanks for.

Precessional instability in binary black holes with aligned spins

Here we study the stability of black-hole binaries with spins (anti)aligned with the orbital angular momentum. Aligned configurations are points of equilibrium, but are they stable? If the heavier black-hole is aligned and the lighter one is anti-aligned, this turns out to be unstable! And the onset of this instability can be in the LIGO or LISA band!

Davide Gerosa, Michael Kesden, Richard O’Shaughnessy, Antoine Klein, Emanuele Berti, Ulrich Sperhake, Daniele Trifirò.
Physical Review Letters 115 (2015) 141102.
arXiv:1506.09116 [gr-qc].
Selected as PRL Editors’ Suggestion.
Supporting material available here.