Astrophysical Investigations of Dynamical Chern–Simons Theory

  • Awardees
  • Stephon Alexander, Ph.D. Brown University
  • Nicolás Yunes, Ph.D. University of Illinois at Urbana-Champaign
Year Awarded


Stephon Alexander
Brown University
Nicolás Yunes
University of Illinois at Urbana-Champaign

This project will focus on dynamical Chern–Simons gravity. This is an effective field theory that has well-motivated completions at higher energies. It leads to new predictions beyond Einstein’s general relativity, with an impact on understanding of black holes, dark matter, singularities and dark energy.

Physicist and musician Stephon Alexander has straddled the worlds of theoretical physics and jazz music over the last two decades. He works on the connection between the smallest and largest entities in the universe, pushing Einstein’s theory of curved space-time to extremes, beyond the big bang with subatomic phenomena. Alexander is a professor of physics at Brown University, with previous appointments at Stanford University, Imperial College, Penn State, Dartmouth College and Haverford College. Alexander is a specialist in the field of string cosmology, where the physics of superstrings are applied to address longstanding questions in cosmology. In 2001, he co-invented the model of inflation based on higher-dimensional hypersurfaces in string theory called D-branes. In such models, the early universe emerged from the destruction of a higher dimensional D-brane which ignites a period of rapid expansion of space often referred to as ‘cosmic inflation.’ Alexander is also the author of the bestselling books The Jazz of Physics and Fear of a Black Universe.

Nicolás Yunes’ research spans black holes, neutron stars, gravitational waves and tests of general relativity with compact objects. He is well-known for his creation of an agnostic framework to constrain modified gravity, the parameterized post-Einsteinian framework, which is used today to carry out tests of general relativity with gravitational waves. He is also well-known for the discovery of quasi-universal relations of neutron stars, which have been used to infer their radius with gravitational wave observations. Yunes is active in the modeling of gravitational waves from coalescing binaries in the inspiral and ringdown regime through the use of the post-Newtonian approximation and black hole perturbation theory both within and outside general relativity. For example, this work enabled the construction of accurate models for the gravitational waves emitted by generic binaries in dynamical Chern–Simons gravity and other modified gravity theories. Yunes discovered the first spinning black hole solutions in this theory and created the first description of the inspiral for quasi-circular binaries in this theory, which sowed the seeds for a more detailed and higher post-Newtonian order treatment as well as subsequent numerical relativity simulations. Yunes has also authored books both for the general public on how we test general relativity with astrophysical observations, as well as for advanced undergraduate and graduate students on the applications of gravitational waves to fundamental physics, astrophysics and nuclear physics.

Subscribe to MPS announcements and other foundation updates