2026 Simons Collaboration on Black Holes and Strong Gravity Annual Meeting

The Simons Collaboration on Black Holes and Strong Gravity held its inaugural annual meeting at the Simons Foundation in New York on May 7–8, 2026. This was the first collaboration-wide gathering: an opportunity to bring the broader network together, introduce the scientific structure of the collaboration, and begin turning a set of connected research directions into a working community.

There were 118 in-person participants from around the world, including all 12 PIs and all members of the External Advisory Board. The meeting brought together researchers from gravitational physics, general relativity, gravitational-wave data analysis, numerical relativity, analytical relativity, black hole perturbation theory, self-force and extreme-mass-ratio inspirals, gravitational-wave detectors, BHEX and EHT astrophysics, black hole theory, neutron star theory, and high-energy theory. More details on the program can be found on the Simons Foundation meeting page.

The meeting began with an overview by Director Yunes, who introduced the scientific vision of the collaboration and its organizing question: how nonlinear, dynamical strong gravity behaves in nature, within and beyond Einstein’s theory, and how this behavior can be robustly extracted from gravitational-wave observations. The talk emphasized that the collaboration is not starting from zero: working groups, seminars, internal reports, community structures, and communication tools are already in place. At the same time, this was the first opportunity for the broader collaboration to see the whole scientific map at once and identify where to plug in.

The first scientific talks focused on the structure of strong gravity in general relativity. Gary Horowitz reviewed recent developments in extremal and near-extremal black holes, including instabilities and the breakdown of effective field theory in regimes where black holes approach extremality. Alex Lupsasca discussed the deep connection between black hole photon rings and gravitational ringdown, linking observables from black hole imaging and gravitational-wave spectroscopy through the common language of null geodesics, quasinormal modes, and the eikonal limit.

The next set of talks moved toward strong gravity beyond general relativity and the modeling challenge. Katy Clough described new physics in the strong-field regime, emphasizing the importance of nonlinear effects and fully consistent numerical simulations in theories beyond general relativity. Vitor Cardoso reviewed black hole spectroscopy and near-horizon physics, highlighting how gravitational-wave observations can test whether dynamical collapse and ringdown are described by classical general relativity, or whether new effects may become visible in the strong-field regime.

The second day focused on observations, inference, and the problem of extracting reliable physics from real data. Neil Cornish discussed the challenge of dissecting gravitational-wave signals in order to isolate strong-gravity phenomena, such as precession, kicks, tails, memory, and possible effects beyond general relativity, while remaining alert to instrumental and noise artifacts. Jonathan Gair described the complementary population-level problem: how to combine many observations to identify weak strong-gravity signatures across catalogs while controlling modeling assumptions, between-source variability, detector variability, and model misspecification.

The final talk, by Daniel Holz, was deliberately half scientific overview and half community discussion. Holz framed black holes as precision strong-gravity laboratories and then was joined by Yunes to lead a broader conversation about the future of the collaboration: what we should do next, what we should change, what anxieties the community has, and what opportunities people are most excited about. This discussion was an important part of the meeting, because the goal was not only to present results, but to begin shaping the collaboration’s scientific culture and priorities.

Several themes emerged across the two days. First, the strong-gravity problem now requires a genuine loop between theory, modeling, computation, and data analysis. Second, the collaboration must avoid working-group silos by creating concrete cross-disciplinary projects. Third, future gravitational-wave observations, black hole imaging, and precision tests will only be scientifically useful if the community develops robust theoretical dictionaries and data-analysis tools before the relevant data arrive. Finally, the collaboration’s early-career researchers, visitors, seminars, workshops, and shared tools are not peripheral activities; they are the connective tissue through which the collaboration will become scientifically productive.

After the formal meeting concluded, most participants continued discussions at the Flatiron Institute. These informal conversations were an important extension of the meeting itself, allowing smaller groups to form around possible projects, working-group priorities, future visits, and concrete scientific connections.

The Simons Collaboration on Black Holes and Strong Gravity thanks the Simons Foundation for its support, hospitality, and organization. The meeting made clear that the collaboration has a timely scientific center, a broad and engaged community, and a real opportunity to build the common language and shared infrastructure needed to understand gravity in its strongest and most dynamical regimes.

Vitor Cardoso
Niels Bohr Institute

Listening to Black Holes
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One of the most remarkable possibilities of general relativity concerns gravitational collapse to black holes. Is the strong field dynamical regime of gravity well described by general relativity? In this talk, Vitor Cardoso will summarize the status of black hole spectroscopy and attempts at probing near horizon physics.
 

Katy Clough
Queen Mary University of London

New Physics in the Strong Field Regime
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Katy Clough’s recent numerical work has shown the importance of including non-linear effects that modify the gravitational sector in the strong field regime in beyond GR theories, with PN predictions becoming unreliable over the late inspiral-merger phase. Combining the expertise of the collaboration in mathematically well posed formulations, numerics, and data analysis, Clough can now extend her studies to a representative subset of theories, and stress-test current diagnostic and modelling tools with fully consistent waveforms.
 

Neil Cornish
Montana State University

Observing Strong Gravity Phenomena: Dissecting Signals and Separating Interesting Effects From Noise

Theory predicts many interesting strong gravity effects both within and beyond general relativity. As the sensitivity of the detectors improves, it becomes possible to take apart gravitational wave signals and search for strong gravity phenomena such as spin precession, kicks, diffraction, and hereditary effects such as tails and memory. Our goal is to take signals apart and isolate these contributions to the signals, and also, to search for new effects that go beyond the predictions on general relativity. But we have to be sure that what appear to be interesting new effects are not just noise artifacts, due to non-Gaussian or non-stationary instrument noise. Neil Cornish will describe some of the newly developing techniques to dissect gravitational wave signals and go beyond the simplistic noise models that have been used in most previous analyses.
 

Jonathan Gair
Albert Einstein Institute

Connections in the Crowd: Challenges in Identifying Strong Gravity Features Across Populations
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As gravitational wave detectors improve in sensitivity, not only will individual sources be observed with ever increasing signal-to-noise ratio, but the total population of observed systems will continuously increase. Multiple observations can in principle be combined hierarchically to find effects that are too weak to be detected at the individual event level, but this procedure is both computationally expensive and impacted by modelling assumptions. Challenges to overcome include modelling the between-source variability efficiently and accurately, performing model-agnostic hierarchical analyses, and building robustness to model misspecification and variability in the detector performance across the population. In this talk, Jonathan Gair will outline some of the computational and conceptual challenges and how they might be addressed over the next few years.
 

Daniel Holz
University of Chicago

Black Holes as Precision Strong Gravity Laboratories

GW150914 ushered in the era of observational strong gravity. That event revolutionized our understanding, representing a leap of many orders of magnitude. With a catalog of hundreds of sources, we are entering a qualitatively new regime of tests of general relativity. GW150914 had SNR=24, which was statistically unusually high for a first event. As the catalog of events grows, it inevitably leads to higher SNR events: the current catalog has 218 confirmed events supplemented by nearly 200 additional candidate signals, and the loudest event is now GW250114 with an SNR=80, allowing for percent-level tests of gravitational waveforms. Furthermore, larger catalogs naturally lead to a broader exploration of parameter space, including a wider range of spins, masses, and mass ratios, each of which provides novel arenas for strong-field tests. In this talk, Daniel Holz will discuss current and future probes of general relativity in its most extreme exemplars.
 

Gary Horowitz
University of California, Santa Barbara

Update on Extremal and Near-Extremal Black Holes

In this talk, Gary Horowitz will discuss some recent developments concerning extremal and near-extremal black holes. These include instabilities of extremal black holes and the breakdown of effective field theory close to near-extremal black holes.
 

Alex Lupsasca
Vanderbilt University

Black Hole Photon Rings and Gravitational Ringdown

Gravitational-wave observations probe the ringdown of a newly formed black hole, as it relaxes to equilibrium through the emission of quasinormal modes. Meanwhile, efforts to image black holes are beginning to target the photon ring, produced by light that executes multiple orbits before escaping to a distant observer. In this talk, Alex Lupsasca will review recent progress in the study of these two phenomena and explain their deep theoretical connection in the eikonal limit.
 

Nicolás Yunes
University of Illinois Urbana-Champaign

The Simons Collaboration on Black Holes and Strong Gravity: Vision and Opportunities

Black holes provide our clearest laboratory for studying gravity in its most nonlinear and dynamical regime. With rapid progress in mathematical relativity, numerical simulation, data analysis, and gravitational-wave astronomy, we are now in a position to ask sharper questions about what happens when gravity is pushed to its limits and how those answers can be extracted from data. The Simons Collaboration on Black Holes and Strong Gravity was created to bring these threads together. Its central aim is to unite theory, computation, and observation in order to understand strong gravity in Einstein’s theory, explore well-motivated extensions beyond it, and develop robust methods to search for new signatures in gravitational-wave observations. In this opening talk, I will outline the scientific vision of the collaboration, the structure of its main research directions, and the opportunities that lie ahead at the interface of black-hole physics, strong-field gravity, and data-driven discovery. Nicolás Yunes will also discuss the broader goal of building a shared intellectual framework and community that can help shape the future of strong-gravity science.

Watch a playlist of all presentations from this meeting here.