Approximate helical symmetry in compact binaries
The inspiral of a circular, non-precessing binary exhibits an approximate helical symmetry. The effects of eccentricity, precession, and radiation reacti...
Posts by Year
Browse by: Category Tags Year#2024
Fonts/sizes in matplotlib figures for LaTeX publications
Here are a few tips for making your matplotlib figures look really “right” in a LaTeX publication.
Reuse ssh connections for hosts with 2FA (with emacs bonus)
The ssh protocol is smart enough that you can open a control ‘master’ connection and reuse it to logically “connect” to the same machine as many times as you...
Fetch github PRs from the command line
TL;DR For a single repo, add a special “refspec” for a remote (e.g. upstream): git config --add remote.upstream.fetch "+refs/pull/*/head:refs/pullreqs/*" wh...
High-Precision Ringdown Surrogate Model for Non-Precessing Binary Black Holes
Highly precise and robust waveform models are required as improvements in detector sensitivity enable us to test general relativity with more precision t...
A Review of Gravitational Memory and BMS Frame Fixing in Numerical Relativity
Gravitational memory effects and the BMS freedoms exhibited at future null infinity have recently been resolved and utilized in numerical relativity simu...
Imprints of Changing Mass and Spin on Black Hole Ringdown
We numerically investigate the imprints of gravitational radiation-reaction driven changes to a black hole’s mass and spin on the corresponding ringdown ...
Can a radiation gauge be horizon-locking?
In this short Note, I answer the titular question: Yes, a radiation gauge can be horizon-locking. Radiation gauges are very common in black hole perturbat...
Optimizing post-Newtonian parameters and fixing the BMS frame for numerical-relativity waveform hybridizations
Numerical relativity (NR) simulations of binary black holes provide precise waveforms, but are typically too computationally expensive to produce wavefor...
#2023
Notes: Magnetostatic multipole expansion using STF tensors
How to do the STF multipole expansion of the magnetic potential and field (it’s been on my TODO list for a while)
Numerical relativity surrogate model with memory effects and post-Newtonian hybridization
Numerical relativity simulations provide the most precise templates for the gravitational waves produced by binary black hole mergers. However, many of t...
Numerical simulations of black hole-neutron star mergers in scalar-tensor gravity
We present a numerical-relativity simulation of a black hole - neutron star merger in scalar-tensor (ST) gravity with binary parameters consistent with t...
Nonlinear ringdown in the news
Our latest paper, Nonlinearities in black hole ringdowns, was just published in Physical Review Letters! This article was selected as an ❦ Editors’ Suggesti...
Sloan Research Fellowship
I am honored to have been selected as one of this year’s Sloan Research Fellows!
#2022
Nonlinearities in black hole ringdowns
This article was selected as an ❦ Editors’ Suggestion, and Featured in APS’s Physics magazine. More press coverage links here.
Fixing the BMS Frame of Numerical Relativity Waveforms with BMS Charges
The Bondi-van der Burg-Metzner-Sachs (BMS) group, which uniquely describes the symmetries of asymptotic infinity and therefore of the gravitational waves...
Gravitational-wave energy and other fluxes in ghost-free bigravity
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...
Tidally-induced nonlinear resonances in EMRIs with an analogue model
One of the important targets for the future space-based gravitational wave observatory LISA is extreme mass ratio inspirals (EMRIs), where long and accur...
#2021
High Precision Ringdown Modeling: Multimode Fits and BMS Frames
Quasi-normal mode (QNM) modeling is an invaluable tool for characterizing remnant black holes, studying strong gravity, and testing general relativity. ...
Action-angle variables of a binary black-hole with arbitrary eccentricity, spins, and masses at 1.5 post-Newtonian order
Accurate and efficient modeling of the dynamics of binary black holes (BBHs) is crucial to their detection through gravitational waves (GWs), with LIGO/V...
Notes: How to take a derivative of a generalized continued fraction
So you have a function in terms of a continued fraction, and you want to compute its derivative…
Surprises in a classic boundary-layer problem
We revisit a textbook example of a singularly perturbed nonlinear boundary-value problem. Unexpectedly, it shows a wealth of phenomena that seem to have ...
Numerical renormalization group-based approach to secular perturbation theory
Perturbation theory is a crucial tool for many physical systems, when exact solutions are not available, or nonperturbative numerical solutions are intra...
Fixing the BMS frame of numerical relativity waveforms
Understanding the Bondi-Metzner-Sachs (BMS) frame of the gravitational waves produced by numerical relativity is crucial for ensuring that analyses on su...
APS 2021 talk slides: Energy carried by gravitational waves in bimetric gravity
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...
Comparing Remnant Properties from Horizon Data and Asymptotic Data in Numerical Relativity
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...
Constraining gravitational wave amplitude birefringence and Chern-Simons gravity with GWTC-2
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...
#2020
Integrability of eccentric, spinning black hole binaries up to second post-Newtonian order
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.
Brans-Dicke theory in Bondi-Sachs form: Asymptotically flat solutions, asymptotic symmetries and gravitational-wave memory effects
We study the structure of asymptotic null infinity in the Brans-Dicke theory of gravity
A fixed point for black hole distributions
Merger dynamics create an attractive fixed-point in the space of distributions
qnm talk (and notebook) at the BHPToolkit spring 2020 workshop
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...
Numerical relativity simulation of GW150914 beyond general relativity
The first astrophysically-relevant numerical simulation of merging black holes in a higher-curvature theory beyond GR.
Notes: Generalized harmonic form of Einstein’s equations from a gauge-fixed action
The generalized harmonic formulation can be derived by adding a gauge-fixing term to the Einstein-Hilbert action
Poincaré section clicker for the double pendulum
Interactive toy for understanding Poincaré sections and chaos
#2019
Location of the last stable orbit in Kerr spacetime
The dividing line between bound and plunging orbits is an algebraic variety
qnm: A Python package for calculating Kerr quasinormal modes, separation constants, and spherical-spheroidal mixing coefficients
qnm is an open-source Python package for computing the Kerr quasinormal mode frequencies, angular separation constants, and spherical-spheroidal mixing coeff...
Titanium Physicists podcast episode 80 External link
Hear me, Katie Bouman, and friends talk about how to snap a picture of a black hole with the Event Horizon Telescope!
Numerical binary black hole collisions in dynamical Chern-Simons gravity
The first numerical beyond-GR binary black hole merger simulation.
Notes: A family of ramp functions and the Beta function
Sometimes in a numerical method, you need to be able to continuously turn a calculation on or off in space or time.
Surrogate models for precessing binary black hole simulations with unequal masses
A surrogate model extending the parameter space range of fully precessing quasicircular inspirals
The SXS Collaboration catalog of binary black hole simulations
Accurate models of gravitational waves from merging black holes are necessary for detectors to observe as many events as possible while extracting the maximu...
On the Starts with a Bang Podcast! External link
I’m on Episode 42 of the Starts with a Bang Podcast
Talk on the Latin American Webinar on Physics External link
Want to hear me talk about numerical relativity and theories beyond GR?
#2018
The binary black hole explorer: on-the-fly visualizations of precessing binary black holes
Real-time interactive visualizations of merging black holes in seconds!
High-accuracy mass, spin, and recoil predictions of generic black-hole merger remnants
Modeling black holes remnants directly from numerical relativity
Measuring stochastic gravitational-wave energy beyond general relativity
Gravity theories beyond general relativity (GR) can change the properties of gravitational waves: their polarizations, dispersion, speed, and, importantly, e...
Black holes, gravitational waves and fundamental physics: a roadmap
The grand challenges of contemporary fundamental physics—dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities an...
Black hole scalar charge from a topological horizon integral in Einstein-dilaton-Gauss-Bonnet gravity
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...
(Notes) When is a metric conformal to Ricci-flat?
Integrability conditions when trying to solve for a conformal factor
Black-hole kicks from numerical-relativity surrogate models
Modeling black holes’ kicks directly from numerical relativity
Deformation of extremal black holes from stringy interactions
Finding the shape of extremal black holes in beyond-GR theories
#2017
Complex polynomial roots toy
Interactive toy for visualizing relationship between polynomial roots and coefficients
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...
Living Reviews in Relativity author index
I missed the author index from LRR, so I rebuilt one.
Note on simple(r) equations for Einstein-dilaton-Gauss-Bonnet and dynamical Chern-Simons theories
Here to save you some algebra and column-inches
Recent talks in Rome and Nottingham
Just an update on talks I gave recently. Valeria Ferrari, Leonardo Gualtieri, and Paolo Pani hosted the conference “New Frontiers in Gravitational-Wave Astr...
Separating metric perturbations in near-horizon extremal Kerr spacetimes
Whenever you’ve got symmetry, you should use it!
Numerical binary black hole mergers in dynamical Chern-Simons: I. Scalar field
One of the first numerical simulations of black hole mergers in beyond-GR effective field theories
Note on commutation coefficients in two ways
An identity between vector commutation coefficients and coframe connection coefficients
Note on exterior, interior, and Lie derivative superalgebra
These three objects form a superalgebra! Whoa!
ssh ipython notebook tunneling magic
How to get remote jupyter to automatically open a local browser.
Note on Lie derivatives and divergences
When can you integrate-by-parts with Lie derivatives?
Note on generating a divergence identity
Special thanks to Ben Mares for coming up with this identity.
Note on a (dimension-dependent) Weyl 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 ...
TG17 and APS17 talk slides
My talk slides/movies from TG17 and APS17
Notes on the Weyl, E/B, and 3+1 decompositions of Riemann, and curvature invariants
The Weyl decomposition, further splitting into E/B, and computing in terms of 3+1 objects
Notes on the pullback connection
In an effort to keep myself organized, I decided I should type up some notes I have laying around.
#2016
EHT16 Talk Slides
My talk slides/movies from the EHT16 conference in Cambrige, MA
FF2016 Talk Slides
My talk slides/movies from the FF2016 conference at Northwestern
GR21 Talk Slides
My talk slides/movies from the GR21 conference in NYC
On the Titanium Physicists Podcast AGAIN! External link
I’m on Episode 64 of the Titanium Physicists Podcast
April APS Talk Slides
My talks slides/movies from the 2016 April APS meeting in SLC
Kerr Spherical Photon Orbits
Interactive tool for visualizing spherical/circular photon orbits in Kerr
Elliptic Integrals in Javascript External link
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...
Member-at-large of APS Topical Group on Gravitation
Just one more committee
Quora session on gravitational waves, LIGO, black holes External link
I hosted a Quora session. It went well!
Prescriptions for Measuring and Transporting Local Angular Momenta in General Relativity
Angular momentum is tricky to define in GR! Here’s an approach so that observers can all agree with each others’ measurements.
Black Hole Based Tests of General Relativity
Invited review for CQG Focus Issue
On the Titanium Physicists Podcast! External link
I’m on Episode 62 of the Titanium Physicists Podcast
#2015
Winning at #science With Twitter
That moment when social media creates scientific collaboration
Extremal Black Holes in Dynamical Chern-Simons Gravity
Progress in understanding the structure of extremal black holes in Chern-Simons
A Weight Has Been Lifted
The monster topical review has finally been published!
Challenging the Presence of Scalar Charge and Dipolar Radiation in Binary Pulsars
Not all theories with long-ranged scalar fields produce dipole radiation in binaries
Kerr Calculator V2
Interactive tool to compute Kerr quantities
Kerr ISCO calculator
Interactive tool to compute ISCOs in Kerr
Whitespace Cleanup on Diff Lines in Emacs
If you’re in the intersection of git, emacs, and persnickety about whitespace.
Moved to Caltech
I’m back in Pasadena!
“Slimplectic” Integrators: Variational Integrators for General Nonconservative Systems
A generalization of symplectic integrators to non-conservative dynamics.
Testing General Relativity With Present and Future Astrophysical Observations
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...
#2014
The Principle of Stationary Nonconservative Action for Classical Mechanics and Field Theories
Extending Hamilton’s variational principle to nonconservative systems.
Why I-Love-Q: Explaining why universality emerges in compact objects
Explaining why universality emerges in compact objects.
Rapidly Rotating Black Holes in Dynamical Chern-Simons Gravity: Decoupling Limit Solutions and Breakdown
Numerical solutions for rapidly-rotating dCS black holes show where the weak-coupling expansion breaks down.
Note on Legendre Decomposition of the Pontryagin Density in Kerr
Short note simplifying a calculation in the literature.
Three-Hair Newtonian Relations for Rotating Stars
Universal relations between the Newtonian multipole moments of rotating stars.
Parametrizing and Constraining Scalar Corrections to General Relativity
Connecting observables (pulsar binary pericenter precession and gravitational wave phase) to the parameters and structure of theoretical models.
#2013
Isolated and Binary Neutron Stars in Dynamical Chern-Simons Gravity
Chern-Simons corrections to 1) internal structure (including mass shift) and 2) binary dynamics (including pericenter precession) of neutron stars.
#2012
Probes of Strong-field Gravity (PhD Thesis) External link
MIT PhD thesis of Leo C. Stein
Post-Newtonian, Quasicircular Binary Inspirals in Quadratic Modified Gravity
The post-Newtonian calculation scheme applied to binary inspirals in a broad class of almost-GR theories.
#2011
The Geometry of Hamiltonian Monte Carlo
Applying symplectic geometry to understand and refine Hamiltonian MC.
Bumpy Black Holes in Alternative Theories of Gravity
Parametrizing deviations from purely GR, vacuum black holes.
Nonspinning Black Holes in Alternative Theories of Gravity
The deformation to spherically symmetric black holes under a class of corrections to general relativity.
Effective Gravitational Wave Stress-energy Tensor in Alternative Theories of Gravity
Computing how much energy and momentum gravitational waves carry in a very broad class of almost-GR theories.
Solving the Corner-turning Problem for Large Interferometers
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.
#2010
X-Pipeline: An Analysis Package for Autonomous Gravitational-wave Burst Searches
Autonomous gravitational-wave searches—fully automated analyses of data that run without human intervention or assistance—are desirable for a number of re...
#2006
Coherent Network Analysis Technique for Discriminating Gravitational-wave Bursts From Instrumental Noise
How to overconstrain the problem of discriminating gravitational wave signals from detector noise and glitches.