## Simple slow-rotation neutron star structure solver External link

I’m releasing into the wild a simple code for computing neutron star structure in the slow-rotation expansion to first and second order. This code was origi...

I’m releasing into the wild a simple code for computing neutron star structure in the slow-rotation expansion to first and second order. This code was origi...

How to get remote jupyter to automatically open a local browser.

I just created a repo on github for computing complete elliptic integrals in javascript. The README.md is below, and a demo after that. You might ask yoursel...

If you’re in the intersection of git, emacs, and persnickety about whitespace.

Our latest paper, Nonlinearities in black hole ringdowns, was just published in Physical Review Letters! This article was selected as an ❦ Editors’ Suggesti...

I am honored to have been selected as one of this year’s Sloan Research Fellows!

Hear me, Katie Bouman, and friends talk about how to snap a picture of a black hole with the Event Horizon Telescope!

I’m on Episode 42 of the Starts with a Bang Podcast

Want to hear me talk about numerical relativity and theories beyond GR?

I’m on Episode 64 of the Titanium Physicists Podcast

Just one more committee

I hosted a Quora session. It went well!

I’m on Episode 62 of the Titanium Physicists Podcast

I’m back in Pasadena!

How to do the STF multipole expansion of the magnetic potential and field (it’s been on my TODO list for a while)

So you have a function in terms of a continued fraction, and you want to compute its derivative…

The generalized harmonic formulation can be derived by adding a gauge-fixing term to the Einstein-Hilbert action

Sometimes in a numerical method, you need to be able to continuously turn a calculation on or off in space or time.

Integrability conditions when trying to solve for a conformal factor

Here to save you some algebra and column-inches

An identity between vector commutation coefficients and coframe connection coefficients

These three objects form a superalgebra! Whoa!

When can you integrate-by-parts with Lie derivatives?

Special thanks to Ben Mares for coming up with this identity.

There is a nice 4-dimensional Weyl identity that I can never seem to remember off the top of my head; so I decided I need to write this note so I don’t have ...

The Weyl decomposition, further splitting into E/B, and computing in terms of 3+1 objects

In an effort to keep myself organized, I decided I should type up some notes I have laying around.

Numerical relativity simulations provide the most precise templates for the gravitational waves produced by binary black hole mergers. However, many of t...

We present a numerical-relativity simulation of a black hole - neutron star merger in scalar-tensor (ST) gravity with binary parameters consistent with t...

This article was selected as an ❦ Editors’ Suggestion, and Featured in APS’s Physics magazine. More press coverage links here.

The Bondi-van der Burg-Metzner-Sachs (BMS) group, which uniquely describes the symmetries of asymptotic infinity and therefore of the gravitational waves...

One of the key ingredients for making binary waveform predictions in a beyond-GR theory of gravity is understanding the energy and angular momentum carri...

One of the important targets for the future space-based gravitational wave observatory LISA is extreme mass ratio inspirals (EMRIs), where long and accur...

Quasi-normal mode (QNM) modeling is an invaluable tool for characterizing remnant black holes, studying strong gravity, and testing general relativity. ...

Accurate and efficient modeling of the dynamics of binary black holes (BBHs) is crucial to their detection through gravitational waves (GWs), with LIGO/V...

We revisit a textbook example of a singularly perturbed nonlinear boundary-value problem. Unexpectedly, it shows a wealth of phenomena that seem to have ...

Perturbation theory is a crucial tool for many physical systems, when exact solutions are not available, or nonperturbative numerical solutions are intra...

Understanding the Bondi-Metzner-Sachs (BMS) frame of the gravitational waves produced by numerical relativity is crucial for ensuring that analyses on su...

We present a new study of remnant black hole properties from 13 binary black hole systems, numerically evolved using the Spectral Einstein Code. The mass...

We perform a new test of general relativity (GR) with signals from GWTC-2, the LIGO and Virgo catalog of gravitational wave detections. We search for the...

We show that an eccentric binary of black holes with misaligned spins is integrable at 2PN order. We also construct 4 out of 5 action variables at 1.5PN.

We study the structure of asymptotic null infinity in the Brans-Dicke theory of gravity

Merger dynamics create an attractive fixed-point in the space of distributions

The first astrophysically-relevant numerical simulation of merging black holes in a higher-curvature theory beyond GR.

The dividing line between bound and plunging orbits is an algebraic variety

qnm is an open-source Python package for computing the Kerr quasinormal mode frequencies, angular separation constants, and spherical-spheroidal mixing coeff...

The first numerical beyond-GR binary black hole merger simulation.

A surrogate model extending the parameter space range of fully precessing quasicircular inspirals

Accurate models of gravitational waves from merging black holes are necessary for detectors to observe as many events as possible while extracting the maximu...

Real-time interactive visualizations of merging black holes in seconds!

Modeling black holes remnants directly from numerical relativity

Gravity theories beyond general relativity (GR) can change the properties of gravitational waves: their polarizations, dispersion, speed, and, importantly, e...

The grand challenges of contemporary fundamental physics—dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities an...

In theories of gravity that include a scalar field, a compact object’s scalar charge is a crucial quantity since it controls dipole radiation, which can be s...

Modeling black holes’ kicks directly from numerical relativity

Finding the shape of extremal black holes in beyond-GR theories

Whenever you’ve got symmetry, you should use it!

One of the first numerical simulations of black hole mergers in beyond-GR effective field theories

Angular momentum is tricky to define in GR! Here’s an approach so that observers can all agree with each others’ measurements.

Invited review for CQG Focus Issue

Progress in understanding the structure of extremal black holes in Chern-Simons

Not all theories with long-ranged scalar fields produce dipole radiation in binaries

A generalization of symplectic integrators to non-conservative dynamics.

A major review on non-GR theories, black holes and neutron stars in non-GR theories, compact binaries in non-GR theories, and pulsar, gravitational-wave, and...

Extending Hamilton’s variational principle to nonconservative systems.

Explaining why universality emerges in compact objects.

Numerical solutions for rapidly-rotating dCS black holes show where the weak-coupling expansion breaks down.

Short note simplifying a calculation in the literature.

Universal relations between the Newtonian multipole moments of rotating stars.

Connecting observables (pulsar binary pericenter precession and gravitational wave phase) to the parameters and structure of theoretical models.

Chern-Simons corrections to 1) internal structure (including mass shift) and 2) binary dynamics (including pericenter precession) of neutron stars.

MIT PhD thesis of Leo C. Stein

The post-Newtonian calculation scheme applied to binary inspirals in a broad class of almost-GR theories.

Applying symplectic geometry to understand and refine Hamiltonian MC.

Parametrizing deviations from purely GR, vacuum black holes.

The deformation to spherically symmetric black holes under a class of corrections to general relativity.

Computing how much energy and momentum gravitational waves carry in a very broad class of almost-GR theories.

Turning an O(n^2) problem into an O(n log n) problem in radio interferometry, similar in spirit to how the fast Fourier transform operates.

Autonomous gravitational-wave searches—fully automated analyses of data that run without human intervention or assistance—are desirable for a number of re...

How to overconstrain the problem of discriminating gravitational wave signals from detector noise and glitches.

I haven’t been posting every time I gave a talk, so here is a sporadic update. I contributed a talk to the 2021 April APS meeting. This talk is a status u...

Last week I gave an invited talk at the Spring 2020 workshop of the Black Hole Perturbation Toolkit (BHPToolkit). The BHPToolkit is a collection of open sou...

Just an update on talks I gave recently. Valeria Ferrari, Leonardo Gualtieri, and Paolo Pani hosted the conference “New Frontiers in Gravitational-Wave Astr...

My talk slides/movies from TG17 and APS17

My talk slides/movies from the EHT16 conference in Cambrige, MA

My talk slides/movies from the FF2016 conference at Northwestern

My talk slides/movies from the GR21 conference in NYC

My talks slides/movies from the 2016 April APS meeting in SLC

Interactive toy for understanding Poincaré sections and chaos

Interactive toy for visualizing relationship between polynomial roots and coefficients

Interactive tool for visualizing spherical/circular photon orbits in Kerr

Interactive tool to compute Kerr quantities

Interactive tool to compute ISCOs in Kerr