August 25, 2025
Congratulations to Robert Wald, Charles H. Swift Distinguished Service Professor in the Department of Physics, the Enrico Fermi Institute, and the College, who has received a 2025 Dirac Medal from the International Centre for Theoretical Physics (ICTP).
This year, the award recognizes theoretical physicists who have redefined our understanding of gravity, who have turned black holes into windows onto the deepest laws of nature. According to the ICTP announcement, these researchers were among the first to use black holes to explore theories on general relativity, quantum gravity, and string theory. “Three different approaches, one common goal: to understand gravity and the deep structure of space-time. Through their research, they have transformed objects long considered abstract and inaccessible into some of the most powerful tools for probing the secrets of the universe.”
Wald has made a range of foundational contributions to the formal structure of gravitational theory, marked by their mathematical rigor and physical importance. One of his most significant results is a prescription of horizon entropy in general diffeomorphism-invariant theories of gravity. Developed further with his student Vivek Iyer, this formalism expresses horizon entropy as a Noether charge associated with diffeomorphism invariance. While central to our modern understanding of black hole thermodynamics, it also laid the foundation for extensions of holographic entanglement entropy to general gravitational theories and its applications. His other contributions in classical general relativity include his work on black hole stability, energy theorems, and cosmic censorship. His formulation of quantum field theory in curved spacetime provides a conceptual and technical framework for understanding phenomena such as Hawking radiation, the Unruh effect, and the renormalization of stress-energy tensors in curved backgrounds.
Wald’s fellow medalists this year are Gary Gibbons, Cambridge University; Gary Horowitz, University of California Santa Barbara; and Roy Kerr, University of Canterbury.