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!

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/ ⚛️🧪🔭

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 ⚛️🧪🔭

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

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.

📄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.

Congrats to SXS member Elias Most (Asst. Prof. at @caltech.edu) on being named one of the 126 Sloan Research Fellows for 2026! www.caltech.edu/about/news/t...

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...

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!

🎉 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

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 🧪⚛️🔭

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

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 🔭🧪⚛️☄️🐚

🎉 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... 🧪⚛️🔭

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/...

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!

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

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).

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

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 🧪⚛️🔭

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 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. ⚛️🧪🔭

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

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... 🧪⚛️🔭

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

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

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! 🧪⚛️🔭

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 ⚛️🧪🔭

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:

(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.

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!

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

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!

Check out this profile of SXS member Elias Most:

Say hello to the Black Hole Perturbation Toolkit! 🧪⚛️🔭

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... 🧪⚛️🔭

We compare our PN and SF results to numerical relativity simulations from the @sxs-collaboration.bsky.social. We find the second-order SF results agree remarkably well with NR simulations for near-comparable mass binaries with mass ratios ~10:1.

Featuring work by SXS member Elias Most (Caltech)! Check out the nice summary in AAS Nova:

🎉 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 🧪⚛️🔭

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! 🧪⚛️🔭

🎉 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 🧪⚛️🔭 #🧮

Peering into the "eccentric" side of black hole binaries through the brand new waveform model, ESIGMAHM! Check it out here: arxiv.org/abs/2409.13866 This new model is calibrated with our catalog of binary black hole numerical relativity simulations. #GravitationalWaves #BBH #eccentricity 🧪 ⚛️ 🔭

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/

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/

*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 🧪🔭⚛️ #🧮

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Hello, world 4-volume!