New $8-million Simons Collaboration on Black Holes and Strong Gravity will decipher secrets encoded in gravitational wave data

Nicolás Yunes to serve as director of 12-institution network that bridges disciplines

The Simons Foundation announced today it will fund a new multidisciplinary multi-institutional collaboration focused on strong gravity. The Simons Collaboration on Black Holes and Strong Gravity will support the work of 12 co-PIs at 12 separate institutions—gravity and black-hole experts working in theoretical physics, mathematics, numerical computation, AI-assisted data analysis, and gravitational wave observation—to develop a robust theoretical framework for deciphering the secrets encoded in gravitational wave (GW) data, including possible extensions to Einstein’s theory of general relativity.

GW science represents one of the best means to probe the physics of strong gravity. Illinois Physics Professor Nicolás Yunes, who will serve as the collaboration’s director, says the time to build this global network of multidisciplinary strong-gravity and black-hole experts is now, as our GW observational capabilities are rapidly advancing. Once planned upgrades to the Advanced LIGO/Virgo/KAGRA gravitational wave detectors are installed in the next few years, the sensitivity of these instruments will double, increasing the volume of the universe we have access to with GW data by a factor of 8.

“We’re moving toward the era of precision gravitational wave physics,” comments Yunes. “This new era must be accompanied by a multidisciplinary effort to deepen our understanding of non-linear gravity. Otherwise, we will miss secrets encoded in the gravitational wave data, or worse, misinterpret our observations and be led in the wrong direction.”

The new collaboration will develop the theoretical framework necessary to demystify persistent astrophysical puzzles, shedding new light on the nature of black holes.Through this work, GW data may be used to elucidate the matter-antimatter asymmetry of the universe, the nature of dark matter, and physics that potentially diverges from Einstein’s theory of general relativity, including the fundamental incompatibilities of quantum mechanics and gravity.

Yunes notes, “Gravity is one of the pillars of theoretical physics. Through our collaboration, we will work to understand gravity in the most dynamic and violent astrophysical environments, when black holes collide, and gravity is dynamical and strongly  nonlinear. Understanding gravity in this extreme environment  can reveal a lot about nature.

“Our focus will be on strong gravity as predicted in Einstein’s theory, strong gravity in proposed theoretical extensions of general relativity, and on how to extract the strong-gravity features from the data to make robust inferences. GWs are unique messengers that can tell us about what’s happening with strong gravity in these extreme environments.”

Strong gravity describes the physics underlying the most violent and dynamic environments in the universe, such as the inspiral, merger, and ringdown of binary black holes. These cataclysmic events release immense energy in the form of gravitational waves (GWs), ripples in spacetime that travel at the speed of light, squeezing and stretching everything in their path until the black hole relaxes back to equilibrium. Albert Einstein predicted the existence of GWs in 1919 as part of his theory of general relativity. LIGO first detected GWs in 2015, marking the start of the so-called advanced era of GW science. By now, approximately  300 GWs have been observed, most of them from colliding black holes, though neutron star mergers and black hole/neutron star mergers have also been detected. In the next 5 years, the number of GW observations is expected to increase by an order of magnitude Ground-based GW detectors are distributed globally, forming a network that allows scientists to triangulate the location and source of these cosmic space-time ripples. Advanced LIGO in the U.S. has two detectors, one in Livingston, LA, and one in Hanford, WA. These are synced up with Virgo near Pisa, Italy, and with KAGRA in the Kamioka mine in Japan. When the Advanced LIGO/Virgo/KAGRA network finishes Run 04 in October, 2025, the detectors will shut down to install major upgrades prior to the start of Run 05, slated to begin in 2027. The planned upgrades to Advanced LIGO/Virgo/KAGRA’s detectors will double their sensitivity and reach into the cosmos—enabling the identification of more distant GW sources and providing more detailed data for closer GW sources. Additionally, there are plans for a third LIGO detector in India, and funding is in place for an eventual space-based detector called LISA. Next-generation ground-based detectors are also being proposed. The so-called precision era of GW science is coming.

The greater sensitivity of GW detectors that will enable the collection of this more precise GW data will require more precise models to separate the signal from the noise. Models that fail to account for the presence or absence of an accretion disk, the presence of a third astrophysical body in the vicinity of a black-hole merger, instrumental artifacts, and fluctuations in the noise, may force us to miss or misinterpret the most interesting potential discoveries.

“We will develop advanced Bayesian inference and AI-based analyses to robustly detect new non-linear, strong-gravity features in realistic instrumental noise,” says Yunes.

The collaboration will perform analytical calculations, run computer simulations, and test these against observations. The ultimate goal is to develop models—smoking-gun signals to look for in GW data—to decipher the secrets hidden within the observations.

The $8 million grant will bring together  a total of 12 co-PIs at 12 institutions, providing postdoctoral and graduate-student support, as well as travel between member institutions and various meetings per year. In addition to the 12 co-PIs, the collaboration will enlist the expertise of associates: physicists, mathematicians, and data scientists whose research programs are already immersed in these astrophysical  mysteries. These associates include professors at the co-PIs’ institutions, including at Illinois, as well as at over 20 other institutions. Researchers from this large, combined network will come together to tackle the deepest mysteries about our strong gravity universe. 

Yunes will serve as director for the full four-year tenure of this grant. Four co-PIs will join him on the collaboration’s executive committee, each serving a two-year term. An external advisory board of notable scholars will help to set research directions. Members of the network will form working groups to tackle specific subsets of the collaboration’s mission.

The 12 co-PIs include Yunes at Illinois, Emanuele Berti of Johns Hopkins University, Vitor Cardoso of the Niels Bohr Institute,  Katy Clough of Queen Mary, University of London,  Neil Cornish of Montana State University, Jonathan Gair of the Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Daniel Holz of the University of Chicago, Gary Horowitz of the University of California Santa Barbara, Luis Lehner of the Perimeter Institute of Theoretical Physics in Canada, Alex Lupsasca of Vanderbilt University in Nashville, TN, Matias Zaldarriaga of the Institute for Advanced Study in Princeton, NJ, and  Mihalis Dafermos of Princeton University. These co-PIs are physicists and mathematicians who specialize in strong gravity from theoretical, computational and observational perspectives.

In a press release issued today, the Simons Foundation comments, “Through observational advances and breakthroughs in theoretical modeling and data analysis, the study of strong gravity has become a mature and rapidly expanding field. The Simons Collaboration on Black Holes and Strong Gravity will bring together physicists, mathematicians, computer scientists and observers to ensure that strong gravity discoveries are not lost in the explosion of new gravitational observations.”

Yunes notes, “We are very grateful to the Simons Foundation for recognizing the need for a large-scale, organized effort devoted to strong gravity that includes many key players around the globe.Our co-PIs are at the forefront of innovation in perturbation theory, mathematical relativity, numerical relativity, observational gravity, Bayesian data analysis, and machine learning.”