SXS Collaboration
@sxs-collaboration.bsky.social
We develop and run supercomputer code for numerically simulating black holes, neutron stars, and beyond.
SXS = Simulating eXtreme Spacetimes
🌐 https://www.black-holes.org/
SXS = Simulating eXtreme Spacetimes
🌐 https://www.black-holes.org/
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
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🔒 journals.aps.org/prl/abstract...
🔓 arxiv.org/abs/2504.15978
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September 2, 2025 at 7:25 PM
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
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🔒 journals.aps.org/prl/abstract...
🔓 arxiv.org/abs/2504.15978
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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
August 29, 2025 at 7:08 PM
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
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
August 29, 2025 at 7:04 PM
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
Eight pages of the new paper are dedicated to studying the quality of our waveforms! For example, one of our plots shows how well different angular harmonics are converging (we provide all the way up to ℓ=8). Our median waveform difference between resolutions is 4*10^-4.
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May 20, 2025 at 3:13 AM
Eight pages of the new paper are dedicated to studying the quality of our waveforms! For example, one of our plots shows how well different angular harmonics are converging (we provide all the way up to ℓ=8). Our median waveform difference between resolutions is 4*10^-4.
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The median simulation length is 22 orbits, while the longest is 148 orbits. Here’s a visual overview of the before and after of our parameter-space coverage:
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May 20, 2025 at 3:13 AM
The median simulation length is 22 orbits, while the longest is 148 orbits. Here’s a visual overview of the before and after of our parameter-space coverage:
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This data is freely available via data.black-holes.org and through the sxs package for python (installable via your favorite package manager, see sxs.rtfd.io for docs). Here’s a sampling of some more extreme systems in our catalog, showcasing a lot of the physics we can capture:
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May 20, 2025 at 3:13 AM
This data is freely available via data.black-holes.org and through the sxs package for python (installable via your favorite package manager, see sxs.rtfd.io for docs). Here’s a sampling of some more extreme systems in our catalog, showcasing a lot of the physics we can capture:
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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.
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May 20, 2025 at 3:13 AM
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.
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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.
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May 12, 2025 at 8:31 PM
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.
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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...
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May 7, 2025 at 5:55 PM
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...
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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
📄 arxiv.org/abs/2502.02739
April 7, 2025 at 4:10 PM
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
📄 arxiv.org/abs/2502.02739
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
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
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
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
🎉 Publication day! 🎉
This review, by members of SXS, is now published in Classical and Quantum Gravity. And, it's Open Access!
A review of gravitational memory and BMS frame fixing in numerical relativity
🔓 CQG: iopscience.iop.org/article/10.1...
🔓 arXiv: arxiv.org/abs/2405.08868
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This review, by members of SXS, is now published in Classical and Quantum Gravity. And, it's Open Access!
A review of gravitational memory and BMS frame fixing in numerical relativity
🔓 CQG: iopscience.iop.org/article/10.1...
🔓 arXiv: arxiv.org/abs/2405.08868
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October 22, 2024 at 2:17 PM
🎉 Publication day! 🎉
This review, by members of SXS, is now published in Classical and Quantum Gravity. And, it's Open Access!
A review of gravitational memory and BMS frame fixing in numerical relativity
🔓 CQG: iopscience.iop.org/article/10.1...
🔓 arXiv: arxiv.org/abs/2405.08868
🧪⚛️🔭
This review, by members of SXS, is now published in Classical and Quantum Gravity. And, it's Open Access!
A review of gravitational memory and BMS frame fixing in numerical relativity
🔓 CQG: iopscience.iop.org/article/10.1...
🔓 arXiv: arxiv.org/abs/2405.08868
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We're so happy that Mark Scheel, one of the senior members of the SXS collaboration, has been elected a 2024 Fellow of the @apsphysics.bsky.social! Congratulations to Mark!
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October 4, 2024 at 3:33 PM
We're so happy that Mark Scheel, one of the senior members of the SXS collaboration, has been elected a 2024 Fellow of the @apsphysics.bsky.social! Congratulations to Mark!
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The GWs are extracted with Cauchy-Characteristic Evolution (CCE) in which the metric is actually evolved all the way out to future null infinity!
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October 2, 2024 at 7:17 PM
The GWs are extracted with Cauchy-Characteristic Evolution (CCE) in which the metric is actually evolved all the way out to future null infinity!
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In our paper we simulated an equal mass non-spinning BBH through 18 orbits of insprial, merger, and ringdown. We show that our simulations are correct by running at multiple resolutions and demonstrating that the gravitational waves approach the same answer.
Convergence!
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Convergence!
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October 2, 2024 at 7:16 PM
In our paper we simulated an equal mass non-spinning BBH through 18 orbits of insprial, merger, and ringdown. We show that our simulations are correct by running at multiple resolutions and demonstrating that the gravitational waves approach the same answer.
Convergence!
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Convergence!
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The discontinuous Galerkin method lets us to break our computational domain into smaller chunks that can each be worked on independently. When a problem is smooth, DG converges exponentially like spectral. With discontinuities, DG acts like finite element.
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October 2, 2024 at 7:15 PM
The discontinuous Galerkin method lets us to break our computational domain into smaller chunks that can each be worked on independently. When a problem is smooth, DG converges exponentially like spectral. With discontinuities, DG acts like finite element.
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Spectral methods are very efficient for modeling BBH spacetimes because the spacetime metric is smooth. But we also need to be able to parallelize our problem so it can run on larger supercomputers. That’s where discontinuous Galerkin shines.
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October 2, 2024 at 7:14 PM
Spectral methods are very efficient for modeling BBH spacetimes because the spacetime metric is smooth. But we also need to be able to parallelize our problem so it can run on larger supercomputers. That’s where discontinuous Galerkin shines.
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These are the first gravitational waveforms from a binary black hole merger using discontinuous Galerkin methods; done in our open-source SpECTRE NR code (spectre-code.org —which logo do you like more?). Our previous code, SpEC, uses spectral methods. The difference?
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October 2, 2024 at 7:13 PM
These are the first gravitational waveforms from a binary black hole merger using discontinuous Galerkin methods; done in our open-source SpECTRE NR code (spectre-code.org —which logo do you like more?). Our previous code, SpEC, uses spectral methods. The difference?
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🎉 New preprint day! 🎉 This is a big one! First complete binary black hole inspiral, merger, & ringdown using our next-generation code SpECTRE.
Simulating binary black hole mergers using discontinuous Galerkin methods
arxiv.org/abs/2410.00265
Led by Kyle Nelli and Geoffrey Lovelace
1/8 🧪⚛️🔭 #🧮
Simulating binary black hole mergers using discontinuous Galerkin methods
arxiv.org/abs/2410.00265
Led by Kyle Nelli and Geoffrey Lovelace
1/8 🧪⚛️🔭 #🧮
October 2, 2024 at 7:09 PM
🎉 New preprint day! 🎉 This is a big one! First complete binary black hole inspiral, merger, & ringdown using our next-generation code SpECTRE.
Simulating binary black hole mergers using discontinuous Galerkin methods
arxiv.org/abs/2410.00265
Led by Kyle Nelli and Geoffrey Lovelace
1/8 🧪⚛️🔭 #🧮
Simulating binary black hole mergers using discontinuous Galerkin methods
arxiv.org/abs/2410.00265
Led by Kyle Nelli and Geoffrey Lovelace
1/8 🧪⚛️🔭 #🧮
Here are a few visualizations of the numerical simulations used in this study. Read all the details at arxiv.org/abs/2409.09147!
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September 17, 2024 at 5:07 PM
Here are a few visualizations of the numerical simulations used in this study. Read all the details at arxiv.org/abs/2409.09147!
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Move over, neutrons.
Small muons, pions, & neutrinos make a sizeable difference when neutron stars collide!
SXS members Michael Pajkos & Elias Most (@caltech.edu) dive in with this latest preprint: arxiv.org/abs/2409.09147
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Small muons, pions, & neutrinos make a sizeable difference when neutron stars collide!
SXS members Michael Pajkos & Elias Most (@caltech.edu) dive in with this latest preprint: arxiv.org/abs/2409.09147
🧪🔭 ⚛️ 1/
September 17, 2024 at 5:07 PM
Move over, neutrons.
Small muons, pions, & neutrinos make a sizeable difference when neutron stars collide!
SXS members Michael Pajkos & Elias Most (@caltech.edu) dive in with this latest preprint: arxiv.org/abs/2409.09147
🧪🔭 ⚛️ 1/
Small muons, pions, & neutrinos make a sizeable difference when neutron stars collide!
SXS members Michael Pajkos & Elias Most (@caltech.edu) dive in with this latest preprint: arxiv.org/abs/2409.09147
🧪🔭 ⚛️ 1/
Most numerical relativity codes work in a finite volume of spacetime. Cauchy-characteristic evolution is a powerful technique for simulating gravitational waves all the way out to "future null infinity"!
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September 17, 2024 at 4:58 PM
Most numerical relativity codes work in a finite volume of spacetime. Cauchy-characteristic evolution is a powerful technique for simulating gravitational waves all the way out to "future null infinity"!
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Recent preprint from SXS members!
Einstein-Klein-Gordon system via Cauchy-characteristic evolution: Computation of memory and ringdown tail
arxiv.org/abs/2409.06141
Led by Sizheng Ma (Perimeter Inst.)
What's it all about?
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Einstein-Klein-Gordon system via Cauchy-characteristic evolution: Computation of memory and ringdown tail
arxiv.org/abs/2409.06141
Led by Sizheng Ma (Perimeter Inst.)
What's it all about?
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September 17, 2024 at 4:57 PM
Recent preprint from SXS members!
Einstein-Klein-Gordon system via Cauchy-characteristic evolution: Computation of memory and ringdown tail
arxiv.org/abs/2409.06141
Led by Sizheng Ma (Perimeter Inst.)
What's it all about?
🧪⚛️🔭 #🧮 1/
Einstein-Klein-Gordon system via Cauchy-characteristic evolution: Computation of memory and ringdown tail
arxiv.org/abs/2409.06141
Led by Sizheng Ma (Perimeter Inst.)
What's it all about?
🧪⚛️🔭 #🧮 1/
*tap tap tap* Hello, world 4-volume!
We're the Simulating eXtreme Spacetimes collaboration! You may know us from such hits as "What are the gravitational waves from a black-hole neutron-star merger?" or "What would you actually see looking at a black hole binary?"
Image credit: SXS Lensing
🧪🔭⚛️ #🧮
We're the Simulating eXtreme Spacetimes collaboration! You may know us from such hits as "What are the gravitational waves from a black-hole neutron-star merger?" or "What would you actually see looking at a black hole binary?"
Image credit: SXS Lensing
🧪🔭⚛️ #🧮
September 12, 2024 at 8:01 PM
*tap tap tap* Hello, world 4-volume!
We're the Simulating eXtreme Spacetimes collaboration! You may know us from such hits as "What are the gravitational waves from a black-hole neutron-star merger?" or "What would you actually see looking at a black hole binary?"
Image credit: SXS Lensing
🧪🔭⚛️ #🧮
We're the Simulating eXtreme Spacetimes collaboration! You may know us from such hits as "What are the gravitational waves from a black-hole neutron-star merger?" or "What would you actually see looking at a black hole binary?"
Image credit: SXS Lensing
🧪🔭⚛️ #🧮