iiinova — where your digital self keeps evolving

Reposted by SXS Collaboration

keefemitman.bsky.social @keefemitman.bsky.social · 27/05/2026

Hello, world! As a first post, I thought I'd introduce myself; I'm a NASA Einstein Fellow @ Cornell studying gravitational waves as a part of @sxs-collaboration.bsky.social, @ligo.org, and @lisacommunity.bsky.social. I study many aspects of gravity, but my latest ambition has been testing GR!

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2026

Neutron-star mergers are key sites for producing heavy elements through the r-process. Feng et al. investigate how magnetically driven shocks reprocess the ejecta, changing nucleosynthesis and leaving observable signatures in kilonova light curves. 2/2

Panel (a) of the paper, the Early-launch scenario. Caption: Magnetically powered shock–ejecta interaction for different shock strengths. Shown are the final snapshots of the simulations at ct/r0 = 101.5 for the early-launch scenario and ct/r0 = 121.8 for the late-launch scenario, displaying the temperature T (left half) and rest-mass density ρ (right half) in the top panels, and the entropy s (left half) and Lorentz factor γ (right half) in the bottom panels. The shock strength is determined by the initial magnetic-field amplitude, which controls the shock acceleration of the ejecta. From left to right, the shock strength increases, corresponding to maximum Lorentz factors of γmax = 1.58, 2.19, 2.96, and 3.90 for the early-launch case, and γmax = 1.16, 1.30, 1.55, and 1.84 for the late-launch case.

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2026

Check out the latest SXS preprint, led by member Yuan Feng of @caltech.edu! arxiv.org/abs/2605.03947 Effects of magnetically driven shocks on nucleosynthesis and kilonovae from neutron star mergers What's it about? 1/ ⚛️🧪🔭

Fig. 1 from the preprint. Caption: Schematic of the initial setup. A dipolar magnetic field is initialized only inside the truncation radius r0, while the ejecta cloud begins outside this radius. The cloud is decomposed into a dense inner core, r0 < r < rc, and a diffuse fast tail, rc < r < re, with homologous radial expansion.

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SXS Collaboration @sxs-collaboration.bsky.social · 05/05/2026

By performing numerical relativity simulations of hierarchical compact object mergers, this research predicts that in collapsar disks, repeated mergers of neutron star fragments akin to planetary formation dynamics might leave a critical trace of eccentricity in the gravitational wave signal. 2/2

From Fig. 1 of the paper. The result of a numerical simulation starting with two clusters, showing the resulting objects and tracks of their trajectories orbiting around their common center of mass.

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SXS Collaboration @sxs-collaboration.bsky.social · 05/05/2026

Can potential subsolar-mass gravitational wave events reveal their origin? New preprint by SXS researchers @caltech.edu and Cornell: Eccentricity as a signature of hierarchical subsolar-mass mergers in collapsar disks Jiaxi Wu, Elias Most, et al. arxiv.org/abs/2604.26912 What's it about? 1/2 ⚛️🧪🔭

arxiv.org

Eccentricity as a signature of hierarchical subsolar-mass mergers in collapsar disks

In this work, we investigate gravitational-wave signatures of a proposed subsolar-mass merger scenario resulting from fragmentation inside a collapsar accretion disk. This scenario has gained recent i...

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SXS Collaboration @sxs-collaboration.bsky.social · 05/05/2026

If you follow the @sxs-collaboration.bsky.social account, you've probably seen some of Keefe's research before!

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Reposted by SXS Collaboration

Leo C. Stein @duetosymmetry.com · 05/05/2026

Everyone say hi to @keefemitman.bsky.social! Keefe is an expert in black holes, gravitational waves, data analysis, and especially fun things like gravitational memory.

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SXS Collaboration @sxs-collaboration.bsky.social · 30/03/2026

📄New Preprint by Khairnar et al. arxiv.org/abs/2603.24661. ⚛️🧪 Here we improve the robustness of center-of-mass (CoM) frame fixing method for NR waveforms. We reduce the sensitivity of the fitting parameters by modeling the out-spiraling oscillations of the CoM charge using post-Newtonian results.

arxiv.org

Fixing the center-of-mass frame of numerical relativity waveforms using the post-Newtonian center-of-mass charge

The Bondi--van der Burg--Metzner--Sachs (BMS) frame of gravitational waves produced by numerical relativity (NR) simulations is crucial for building accurate waveform models. A proper comparison of NR...

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SXS Collaboration @sxs-collaboration.bsky.social · 10/12/2025

Two of our papers on black-hole scattering have been published in Physical Review D! 🎉 To celebrate, here is a visualisation of the gravitational wave emission from a close scattering encounter: youtu.be/u9wBZEYfyAM Paper 1: doi.org/10.1103/p6fx... Paper 2: doi.org/10.1103/bdsb...

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SXS Collaboration @sxs-collaboration.bsky.social · 16/11/2025

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!

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SXS Collaboration @sxs-collaboration.bsky.social · 06/10/2025

Oh and I forgot to share to the feeds... please share! ⚛️🧪🔭

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SXS Collaboration @sxs-collaboration.bsky.social · 06/10/2025

🎉 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

arxiv.org

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 Einst...

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SXS Collaboration @sxs-collaboration.bsky.social · 02/09/2025

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.

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SXS Collaboration @sxs-collaboration.bsky.social · 29/08/2025

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.

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SXS Collaboration @sxs-collaboration.bsky.social · 29/08/2025

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.

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Reposted by SXS Collaboration

LIGO Scientific Collaboration @ligo.org · 26/08/2025

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 🔭🧪⚛️☄️🐚

youtube.com

Visualization of the GWTC-4.0 events

YouTube video by Max Planck Institute for Gravitational Physics

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SXS Collaboration @sxs-collaboration.bsky.social · 20/08/2025

🎉 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... 🧪⚛️🔭

iopscience.iop.org

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Reposted by SXS Collaboration

Living Reviews | Relativity @livingrev-relativ.bsky.social · 08/08/2025

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/...

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SXS Collaboration @sxs-collaboration.bsky.social · 16/07/2025

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!

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SXS Collaboration @sxs-collaboration.bsky.social · 04/06/2025

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

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Reposted by SXS Collaboration

Olly Long @hyperbolly.bsky.social · 21/05/2025

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).

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Reposted by SXS Collaboration

Leo C. Stein @duetosymmetry.com · 20/05/2025

Bonus: here's an animation I generated showing how the sausage was made. Each frame is one commit from the paper repo.

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

There’s a lot more work to do: higher mass ratios, higher eccentricity, and meeting the accuracy requirements of next-generation detectors. Stay tuned for the next version of our catalog! But for now, check out the latest catalog paper at arxiv.org/abs/2505.13378. 13/13

arxiv.org

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

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

We make it publicly available so everyone has high-quality binary black hole simulation data at their fingertips for their research! Of course, we’re not done yet— 12/13

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

Six years is a long time, so there are too many details to summarize here. You can read about all of them in the new SXS catalog paper. We have already been doing a ton of science with this data (www.black-holes.org/for-research... for a list of paper using SpEC). 11/13

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

Because we generated so much data, we needed a new waveform format, which is typically 6 times more compressed than before. The new format is handled seamlessly by the sxs package, which also fetches and caches waveforms (and other data) as needed. 10/13

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

Out of the 2,018 simulations in the last catalog paper, we deprecated 282. We added 2,020 new non-deprecated simulations (and even uploaded another 112 new but deprecated simulations). 9/13

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

More recent simulations are more accurate than older ones, and some old simulations had issues that were only uncovered recently. Therefore we now deprecate simulations if we need (though the old data remains available, by passing an argument in the sxs package). 8/13

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

Over the years, we made many improvements to the Spectral Einstein Code (SpEC, www.black-holes.org/for-research...) that performed all these simulations (Sec. 3 discusses our methods and some of these improvements). 7/13

black-holes.org

SpEC: Spectral Einstein Code - 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,...

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

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. 6/13

Figure 7 from our new paper, showing how well different angular harmonics converge.

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

Our spectral methods continue to be highly efficient—over 1,000 times more efficient than finite-difference methods of comparable accuracy. We always provide multiple resolutions, so anyone can verify our numerical convergence. 5/13

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

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: 4/13

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

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: 3/13

Figure 1 from our new catalog paper. We accurately capture precession, memory, eccentricity, and high mass ratio systems. For full details, see the paper.

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

This catalog update comes six years after our last catalog (arxiv.org/abs/1904.04831), with too many improvements to list here. Our catalog now has 3,756 simulations, the largest and most accurate numerical relativity catalog to date. 2/13

arxiv.org

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 maximum science. Near the time of merger, the gra...

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SXS Collaboration @sxs-collaboration.bsky.social · 20/05/2025

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 🧪⚛️🔭

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SXS Collaboration @sxs-collaboration.bsky.social · 15/05/2025

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... 🧪⚛️🔭

youtube.com

A visualization of the moving mesh in binary black hole merger inspiral simulation

YouTube video by SXS Collaboration

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SXS Collaboration @sxs-collaboration.bsky.social · 12/05/2025

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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Reposted by SXS Collaboration

LIGO Scientific Collaboration @ligo.org · 09/05/2025

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

media.tenor.com

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

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SXS Collaboration @sxs-collaboration.bsky.social · 07/05/2025

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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SXS Collaboration @sxs-collaboration.bsky.social · 07/04/2025

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

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SXS Collaboration @sxs-collaboration.bsky.social · 02/03/2025

Also, how do we feel about this account's handle? Should we switch to using our domain, becoming @black-holes.org?

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SXS Collaboration @sxs-collaboration.bsky.social · 02/03/2025

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! 🧪⚛️🔭

black-holes.org

Home - SXS

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Reposted by SXS Collaboration

Leo C. Stein @duetosymmetry.com · 21/02/2025

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.

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SXS Collaboration @sxs-collaboration.bsky.social · 11/12/2024

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:

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Reposted by SXS Collaboration

Olly Long @hyperbolly.bsky.social · 08/12/2024

(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.

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Reposted by SXS Collaboration

Olly Long @hyperbolly.bsky.social · 04/12/2024

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!

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SXS Collaboration @sxs-collaboration.bsky.social · 02/12/2024

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

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Reposted by SXS Collaboration

Leo C. Stein @duetosymmetry.com · 01/12/2024

PS The event horizons do totally unintuitive things when the BHs merge. Check out this simulation from the @sxs-collaboration.bsky.social: youtu.be/Y1M-AbWIlVQ?.... This comes from the mathematical definition of event horizons depending on the whole future history of the universe!

youtu.be

Event horizons of merging black holes with 6 to 1 mass ratio

YouTube video by SXS Collaboration

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