SXS Collaboration
LightNews LightNews
banner
sxs-collaboration.bsky.social
SXS Collaboration
@sxs-collaboration.bsky.social
380 followers 64 following 58 posts
We develop and run supercomputer code for numerically simulating black holes, neutron stars, and beyond.

SXS = Simulating eXtreme Spacetimes

🌐 https://www.black-holes.org/
Posts Replies Media Videos
sxs-collaboration.bsky.social
Our latest paper explores what happens when we push numerical relativity to the extreme when simulating black-hole scattering with the Spectral Einstein Code (SpEC). Check out this thread by the lead author to find out more!
hyperbolly.bsky.social Olly Long @hyperbolly.bsky.social · 8h
How much information can we gain by pushing numerical relativity to its limit by simulating black hole scattering encounters? My latest paper (below) explores these extreme regions of the black-hole scattering parameter space using simulations generated using the Spectral Einstein Code (SpEC).
Black-hole scattering with numerical relativity: Self-force extraction and post-Minkowskian validation
The asymptotic nature of unbound binary-black-hole encounters provides a clean method for comparing different approaches for modeling the two-body problem in general relativity. In this work, we use n...
arxiv.org
November 16, 2025 at 11:35 AM
sxs-collaboration.bsky.social
🎉 Happy paper publication day! 🎉 Our third catalog of binary black hole simulations, now published in Classical and Quantum Gravity. And it's open access!

Scheel et al. 2025 Class. Quantum Grav. 42 195017
iopscience.iop.org/article/10.1...

Also on the @arxiv.bsky.social at arxiv.org/abs/2505.13378
October 6, 2025 at 3:53 PM
sxs-collaboration.bsky.social
Just published in Physical Review Letters! Check out this article by SXS researchers Boyeneni, Wu and Most (@caltech.edu) on interpreting colliding black holes similar to the attraction of two electric charges.
🔒 journals.aps.org/prl/abstract...
🔓 arxiv.org/abs/2504.15978

🧪⚛️🔭
Rapidly spinning Kerr black hole in a dynamically evolved moving puncture gauge. Shown in color are the gravitational energy density and toroidal magnetic field in the meridional plane. Streamlines indicate the static component of the gravitational electric field and magnetic fields. The black ellipse marks the black hole horizon; white dashed contours denote the ergosphere.
September 2, 2025 at 7:25 PM
sxs-collaboration.bsky.social
Cranking up the temperature! SXS researchers Hai-Yang Wang, Elias Most and Philip Hopkins (@caltech.edu) show how hot flows around supermassive black hole binaries with strong magnetic fields alter their feeding behavior. Full results at arxiv.org/abs/2508.16855
Volume rendering of a circumbinary magnetically arrested accretion disk simulation in a non-erupting state, when the cooling is treated with an adiabatic prescription.
August 29, 2025 at 7:08 PM
sxs-collaboration.bsky.social
Earthquakes on neutron stars?! SXS researchers Louis Burnaz and Elias Most (@caltech.edu) and Ashley Bransgrove (Princeton) simulate how these could be detected in signals from very active radio burst transients. Read their results at arxiv.org/abs/2508.18033
Fluctuations in the toroidal component of the magnetic field (top) and electric field (bottom) in the simulated magnetar quake event.
August 29, 2025 at 7:04 PM
Reposted by SXS Collaboration
ligo.org
A spacetime waltz. Simulations from @sxs-collaboration.bsky.social consistent with our 86 most confident new detections, each showing the orbiting components and their emitted gravitational waves

www.youtube.com/watch?v=3B6W...

🎬I Markin/T Dietrich/H Pfeiffer

#GWTC4 🔭🧪⚛️☄️🐚
Visualization of the GWTC-4.0 events
YouTube video by Max Planck Institute for Gravitational Physics
www.youtube.com
August 26, 2025 at 1:29 PM
sxs-collaboration.bsky.social
🎉 Great news 🎉 — yesterday CQG accepted our third catalog paper!! The accepted manuscript can be found on their site here: iopscience.iop.org/article/10.1...

🧪⚛️🔭
August 20, 2025 at 7:02 PM
Reposted by SXS Collaboration
livingrev-relativ.bsky.social
2025 ICTP Dirac Medal Goes to Gravity Explorers: The award is attributed to four scientists who have turned black holes into windows onto the deepest laws of nature www.ictp.it/news/2025/8/...
2025 ICTP Dirac Medal Goes to Gravity Explorers
August 8, 2025 at 10:01 AM
sxs-collaboration.bsky.social
We now have our first paper on binary black hole scattering simulations generated with the Spectral Einstein Code (SpEC)! For more info on modelling these high-energy systems, see this thread by the lead author!
hyperbolly.bsky.social Olly Long @hyperbolly.bsky.social · Jul 16
What happens when high-velocity black holes hurtle past each other in a close encounter, deflecting through spacetime but never merging? My latest paper (below) presents the first simulations of black hole scattering generated using the Spectral Einstein Code (SpEC). (1/6)
Highly accurate simulations of asymmetric black-hole scattering and cross validation of effective-one-body models
The study of unbound binary-black-hole encounters provides a gauge-invariant approach to exploring strong-field gravitational interactions in two-body systems, which can subsequently inform waveform m...
arxiv.org
July 16, 2025 at 1:52 PM
sxs-collaboration.bsky.social
Check out this article about star quakes and monster shocks — research done by SXS collaboration members Yoonsoo Kim and Elias Most, both at @caltech.edu
caltech.edu Caltech @caltech.edu · Jun 3
To better understand the extreme physics underlying such a grizzly demise, researchers at Caltech are using supercomputers to simulate black hole–neutron star collisions.

www.caltech.edu/about/news/s...
Star Quakes and Monster Shock Waves
Caltech researchers simulate a black hole consuming a neutron star.
www.caltech.edu
June 4, 2025 at 1:29 AM
Reposted by SXS Collaboration
hyperbolly.bsky.social
I’m incredibly proud to be part of this and to have my simulations turn into the first publicly available scattering and dynamical capture waveforms!

Below is a plot I made for the Einstein Toolkit Blue Book (arXiv:2503.12263) showing the waveforms SXS:BBH:3999 (scatter) and SXS:BBH:4000 (capture).
May 21, 2025 at 5:43 AM
Reposted by SXS Collaboration
duetosymmetry.com
Bonus: here's an animation I generated showing how the sausage was made. Each frame is one commit from the paper repo.
May 20, 2025 at 3:43 AM
sxs-collaboration.bsky.social
We are excited to release a major update to our catalog of binary black hole simulations, available at arxiv.org/abs/2505.13378! Such simulations are key to LIGO/Virgo/KAGRA being able to extract science from their gravitational wave detections.

1/13

🧪⚛️🔭
Figure 1 from our new catalog paper. We accurately capture precession, memory, eccentricity, and high mass ratio systems. For full details, see the paper.
May 20, 2025 at 3:13 AM
sxs-collaboration.bsky.social
When simulating orbiting black holes, we move our grid with the holes! One of the key lessons of general relativity is coordinates are meaningless. We exploit this to choose comoving coordinates where the metric changes as little as possible.

www.youtube.com/watch?v=j4WG...

🧪⚛️🔭
A visualization of the moving mesh in binary black hole merger inspiral simulation
YouTube video by SXS Collaboration
www.youtube.com
May 15, 2025 at 9:23 PM
sxs-collaboration.bsky.social
A recent paper led by collaboration members Yoonsoo Kim and Elias Most (both at Caltech) is in @aasnova.org today! This work explores the formation of strongly magnetized "monster" shocks and a transient "black hole pulsar" state from mergers of a magnetized neutron star and a black hole.

⚛️🧪🔭
May 12, 2025 at 8:31 PM
Reposted by SXS Collaboration
ligo.org
When two black holes merge, they form a bigger black hole. The mass of the bigger black hole will be around 95% of the mass of its two parent black holes. The remaining 5% is carried away as the energy in the gravitational waves

#BlackHoleWeek 2/🧵

🎞️: @sxs-collaboration.bsky.social
a black hole in the middle of a galaxy
Alt: Simulation of two black holes merging. They appear black against the background of stars, but the light from the stars is distorted by their gravity
media.tenor.com
May 9, 2025 at 8:17 AM
sxs-collaboration.bsky.social
Happy #BlackHoleWeek! To celebrate, we’re releasing the highest-resolution ray-traced still from one of our simulations to date. This skeet has a low res preview. To zoom into the full 43,200 × 21,600 pixel rendering, head to www.black-holes.org/2025/05/07/B...
🧪⚛️🔭
May 7, 2025 at 5:55 PM
sxs-collaboration.bsky.social
A recent paper presents a PN-inspired framework to measure eccentricity directly from gravitational waves 🌊🌀 Focused on non-precessing eccentric BBH mergers, using mode modulations driven by the eccentricity.

📄 arxiv.org/abs/2502.02739
April 7, 2025 at 4:10 PM
sxs-collaboration.bsky.social
Also, how do we feel about this account's handle? Should we switch to using our domain, becoming @black-holes.org?
March 2, 2025 at 7:54 PM
sxs-collaboration.bsky.social
Our web site, www.black-holes.org, has silently re-launched! Now that we're using Jekyll and github pages, we hope to give more frequent updates about our latest research. What do you want to see there? Leave a comment below!
🧪⚛️🔭
Home - SXS
The SXS project is a collaborative research effort involving multiple institutions. Our goal is the simulation of black holes and other extreme spacetimes to gain a better understanding of Relativity,...
www.black-holes.org
March 2, 2025 at 7:53 PM
Reposted by SXS Collaboration
duetosymmetry.com
Wake up babe, new preprint just dropped

Length dependence of waveform mismatch:
a caveat on waveform accuracy
Mitman, Stein, et al.
arxiv.org/abs/2502.14025

⚛️🧪🔭
Screenshot of the title/auth list/abstract: Length dependence of waveform mismatch: a caveat on waveform accuracy Keefe Mitman, Leo C. Stein, Michael Boyle, Nils Deppe, Lawrence E. Kidder, Harald P. Pfeiffer, Mark A. Scheel Abstract. The Simulating eXtreme Spacetimes Collaboration’s code SpEC can now routinely simulate binary black hole mergers undergoing ∼ 25 orbits, with the longest simulations undergoing nearly ∼ 180 orbits. While this sounds impressive, the mismatch between the highest resolutions for this long simulation is O(10^−1). Meanwhile, the mismatch between resolutions for the more typical simulations tends to be O(10^−4), despite the resolutions being similar to the long simulations’. In this note, we explain why mismatch alone gives an incomplete picture of code—and waveform—quality, especially in the context of providing waveform templates for LISA and 3G detectors, which require templates with O(10^3) − O(10^5) orbits. We argue that to ready the GW community for the sensitivity of future detectors, numerical relativity groups must be aware of this caveat, and also run future simulations with at least three resolutions to properly assess waveform accuracy. Fig 2 from the preprint, which shows mismatch (between resolutions) as a function of length of time interval over which the mismatch is computed. There are 4 curves, each going roughly like M ~ t^2. The four curves are in two groups: Two from simulations SXS:BBH:1412, and two from SXS:BBH:1132. Each simulation has two different truncation error comparisons: med vs. low and high vs. med. They both show convergence.
February 21, 2025 at 3:19 AM
sxs-collaboration.bsky.social
Check out this thread from SXS member @duetosymmetry.com about our latest preprint, on finally resolving a very subtle component of gravitational radiation, the tails:
duetosymmetry.com Leo C. Stein @duetosymmetry.com · Dec 11
🎉New paper day🎉 A tale of tails! Finally resolved in fully nonlinear 3+1d numerical relativity with @sxs-collaboration.bsky.social simulations.

Late-time tails in nonlinear evolutions of merging black holes
De Amicis et al.
arxiv.org/abs/2412.06887

What's it all about?
🧪⚛️🔭🧮

1/15
Screenshot of title/author list/abstract of the paper linked in post Figure 1 and caption from the paper. The horz axis is retarded time u after the peak, in units of M. The vertical axis is R|\dot{h}_{20}|/\nu, on a log scale. We see 4 curves, almost exactly on top of each other. Three are from NR simulations at q=1, 2, 3. The fourth is form perturbation theory. They all show an exponentially decaying ringing, followed by a power-law tail. An inset shows the "instantaneous power law index" for each curve, as a function of retarded time, all in rough agreement between -1.5 and -2.
December 11, 2024 at 9:32 PM
Reposted by SXS Collaboration
hyperbolly.bsky.social
(3/7) In 2022, I started my postdoc at the Max Planck Institute for Gravitational Physics (AEI) in Potsdam, Germany. Here, I extended my work to include black hole scattering with comparable masses using Numerical Relativity as part of the @sxs-collaboration.bsky.social.
December 8, 2024 at 10:35 AM
Reposted by SXS Collaboration
hyperbolly.bsky.social
Here is a visualisation of one of my Numerical Relativity simulations with @sxs-collaboration.bsky.social’s Spectral Einstein Code (SpEC).

The initially unbound system loses enough energy at closest approach to become bound leading to a merger. It’s one of the coolest looking simulations I’ve done!
sxs-collaboration.bsky.social SXS Collaboration @sxs-collaboration.bsky.social · Nov 10
Hello, new followers! This account will mostly post about new science from members of the SXS collaboration. Sometimes we make neat visualizations, too! Check out our YouTube channel: www.youtube.com/watch?v=f4Lw...
🧪⚛️🔭
Visualization of a black hole scattering and capture orbit
YouTube video by SXS Collaboration
www.youtube.com
December 4, 2024 at 5:34 AM
sxs-collaboration.bsky.social
Merging supermassive black hole binaries are prime targets for next-generation gravitational wave astronomy.

New GPU-based 3D simulations by SXS researchers Elias Most & Hai-Yang Wang at @caltech.edu reveal strong magnetic fields arresting gas dynamics near the merger.

arxiv.org/abs/2410.23264
December 2, 2024 at 3:15 PM