Illinois physicist awarded $2 million by the Simons Foundation for gravity research

7/2/2021 10:06:20 AM Garrett Williams for ICASU

In the quest to uncover the mysteries of the gravitational universe, the Simons Foundation awarded Illinois Physics Professor Nicolás Yunes a Targeted Grant in Mathematical and Physical Sciences to study astrophysical and cosmological signatures of dynamical Chern-Simons (dCS) gravity. Yunes, who is the founding director of the Illinois Center for Advanced Studies of the Universe (ICASU), shares the $2 million award with Brown University Professor of Physics Stephon Alexander

Artist's impression a neutron star merger and the gravitational waves it creates. (Credit: NASA/Goddard Space Flight Center)
Artist's impression a neutron star merger and the gravitational waves it creates. (Credit: NASA/Goddard Space Flight Center)

As a modified theory of gravity, dCS gravity extends Einstein’s theory of general relativity (GR) by introducing parity-violating interactions. 

 Yunes explains, “GR preserves parity because the laws of physics look the same if you reflect them in a mirror. In dCS gravity this is not the case. Astrophysical objects with a definite handedness (like rotating black holes) are not the same in dCS gravity as their GR counterparts.”

Yunes with graduate students Simone Mezzasoma and Caroline Owen
Professor Yunes (right) works with graduate students Simone Mezzasoma (left) and Caroline Owen. (Credit: L. Brian Stauffer)

If nature is accurately described by dCS gravity, then astrophysical systems with a given handedness—like a spinning black hole or a circularly polarized gravitational wave—would look different than what Einstein’s theory would predict. Astrophysical systems that do not have a preferred handedness, however, like the gravity produced by a non-spinning spherical object, would look in nature just as Einstein’s theory predicts. However, as soon as such a body begins to spin, to move around another object, or to produce gravitational waves, then nature would behave differently than Einstein’s prediction, potentially leading to observable signatures of dCS gravity.

 Yunes and Alexander have already explored dCS gravity extensively. In 2009 they investigated how dCS effects differ from the Einstein model in astrophysical processes, such as the merging of black holes and gravitational wave emissions. The funding provided by the Simons Foundation will allow the collaboration to take the next crucial step in investigating dCS gravity, which is to search for experimental evidence of the model in astrophysical and cosmological data. 

In pursuit of a better understanding of gravity, Alexander will search for signatures of dCS gravity in the cosmological sector, whereas Yunes will focus on signatures in the astrophysical sector. This effort aims to both strengthen ties between the two groups and connect the search for dCS signatures in a more comprehensive manner.

“We hope the research we will undertake will reveal in detail the astrophysical and cosmological signatures of dCS gravity,” says Yunes. “If dCS does accurately predict what happens in nature, we will see its signature in the gravitational wave data from the Laser Interferometer Gravitational Wave Observatory (LIGO) and Virgo. Finding a deviation would be revolutionary, but even a lack of a detection would reveal important information about the properties of gravity in extreme environments.”

Yunes adds, “This award will be instrumental in accomplishing our research goals, because it will provide support for graduate students and postdoctoral scholars focused specifically on such investigations.”

The Yunes group studies a broad set of topics, including black holes; neutron star collisions; the microphysics of neutron stars and their effects on astrophysical objects; and most notably, gravitational waves. The group aims to better understand our gravitational universe in extreme regimes, where the curvature of spacetime is very strong and dynamical. 

The Simons Foundation is a scholarly research organization with a mission to advance the frontiers of research in mathematics and the basics of science. Co-founded in New York City by James and Marilyn Simons, the foundation exists to support basic—or discovery driven—scientific research undertaken in the pursuit of understanding the phenomena of our world.