Leo C. Stein

@duetosymmetry
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531 Posts
Physics Prof @ U of MS. Sloan Fellow. Black holes, gravitational waves, general relativity & beyond. Formerly Caltech, MIT, Cornell. Need thin pizza + fruity coffee. He/him
Webhttps://duetosymmetry.com/
Twitterhttps://twitter.com/duetosymmetry
Githubhttps://github.com/duetosymmetry/
Publicationshttps://inspirehep.net/author/profile/L.C.Stein.2
How does font substitution work for unicode combining characters?

I'm trying to understand how to get emacs to properly combine unicode combining characters when doing font substitution. Here is a concrete example. On my mac, I start emacs -Q, and try to display ...

Emacs Stack Exchange
Do I know anybody who knows Harish-Chandra stuff? Or anybody I don't know who wants to explain some of these things to me?
I updated my notes on the magnetostatic multipole expansion at https://duetosymmetry.com/notes/magnetostatics-stf-mpoles/ — mainly because Cyril Pitrou found an error (1/2 should have been ℓ/(ℓ+1)), and pointed me to Damour+Iyer (1991). Sorry for having wrong notes up for so long!
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)

Leo C. Stein
Last night I was feeling like a grad student as I was deriving the coefficients l/(l+1) and (2l-1)/(2l+1) in this formula (from Blanchet+Damour 1986):
Nice: my CV just hit 69 publications
Bonus: here's an animation I generated showing how the sausage was made. Each frame is one commit from the paper repo.

Something my SXS colleagues and I have been working on for the past six years: https://arxiv.org/abs/2505.13378

The SXS Collaboration's third catalog of binary black hole simulations
Scheel et al.

We have a little news blurb here: https://www.black-holes.org/2025/05/19/catalog-update

Here's a nice figure — read the news blurb for a short explainer, or the paper for more details!

The SXS Collaboration's third catalog of binary black hole simulations

We present a major update to the Simulating eXtreme Spacetimes (SXS) Collaboration's catalog of binary black hole simulations. Using highly efficient spectral methods implemented in the Spectral Einstein Code (SpEC), we have nearly doubled the total number of binary configurations from 2,018 to 3,756. The catalog now densely covers the parameter space with precessing simulations up to mass ratio $q=8$ and dimensionless spins up to $|\vecχ|\le0.8$ with near-zero eccentricity. The catalog also includes some simulations at higher mass ratios with moderate spin and more than 250 eccentric simulations. We have also deprecated and rerun some simulations from our previous catalog (e.g., simulations run with a much older version of SpEC or that had anomalously high errors in the waveform). The median waveform difference (which is similar to the mismatch) between resolutions over the simulations in the catalog is $4\times10^{-4}$. The simulations have a median of 22 orbits, while the longest simulation has 148 orbits. We have corrected each waveform in the catalog to be in the binary's center-of-mass frame and exhibit gravitational-wave memory. We estimate the total CPU cost of all simulations in the catalog to be 480,000,000 core-hours. We find that using spectral methods for binary black hole simulations is over 1,000 times more efficient than much shorter finite-difference simulations of comparable accuracy. The full catalog is publicly available through the sxs Python package and at https://data.black-holes.org .

arXiv.org
🎉 arXiv submission day! 🎉
🎉 Paper acceptance day! 🎉
I was Leo before this Pope