Robert Wald

About

Robert Wald is the Charles H. Swift Distinguished Service Professor in the Department of Physics at The University of Chicago, also affiliated with the Enrico Fermi Institute and the College. His research has been concerned with a broad range of topics in classical general relativity, cosmology, and quantum phenomena related to gravity. A significant focus of his work has been on the theory of black holes and the mathematical and physical analogy between black hole laws and thermodynamics, including the quantum radiation emitted by black holes and its implications for quantum gravity. His interests also include mathematical investigations of classical general relativity, applications to cosmology and astrophysics, and the formulation of quantum field theory in curved spacetime, where gravity is treated classically and other fields quantum mechanically. Wald's work addresses fundamental issues such as the lack of Poincaré symmetry and the absence of a preferred vacuum state in curved spacetime, aiming to contribute to the development of a fully quantum theory of gravity. Additionally, he has conducted research on self-force effects on the motion of small bodies in general relativity, which are crucial for understanding gravitational radiation from phenomena like black hole inspirals. His recent efforts include analyzing the effects of small-scale inhomogeneities in cosmology, developing frameworks to account for nonlinear effects on small scales, and demonstrating that such…

Research topics

• Computer Science
• Theoretical physics
• Physics
• Mathematical physics
• Astronomy
• Astrophysics
• Quantum mechanics
• Mathematics

Selected publications

• Tests of general relativity with binary black holes from the second LIGO-Virgo gravitational-wave transient catalog

  Physical review. D/Physical review. D. · 2021 · 749 citations

  Gravitational waves enable tests of general relativity in the highly dynamical and strong-field regime. Using events detected by LIGO-Virgo up to 1 October 2019, we evaluate the consistency of the data with predictions from the theory. We first establish that residuals from the best-fit waveform are consistent with detector noise, and that the low- and high-frequency parts of the signals are in agreement. We then consider parametrized modifications to the waveform by varying post-Newtonian and p…

  DOI

• Gravitationally mediated entanglement: Newtonian field versus gravitons

  Physical review. D/Physical review. D. · 2022-04-05 · 146 citations

  articleOpen accessSenior author

  We argue that if the Newtonian gravitational field of a body can mediate entanglement with another body, then it should also be possible for the body producing the Newtonian field to entangle directly with on-shell gravitons. Our arguments are made by revisiting a gedankenexperiment previously analyzed by Belenchia et al., which showed that a quantum superposition of a massive body requires both quantized gravitational radiation and local vacuum fluctuations of the spacetime metric in order to a…

  PublisherOA PDFDOI

• Phase effects from strong gravitational lensing of gravitational waves

  Physical review. D/Physical review. D. · 2021-03-22 · 127 citations

  articleOpen accessSenior author

  Assessing the probability that two or more gravitational wave (GW) events are lensed images of the same source requires an understanding of the properties of the lensed images. For short enough wavelengths where wave effects can be neglected, lensed images will generically have a fixed relative phase shift that needs to be taken into account in the lensing hypothesis. For nonprecessing, circular binaries dominated by quadrupole radiation, these lensing phase shifts are degenerate with either a s…

  PublisherOA PDFDOI

• Quantum instability of the Cauchy horizon in Reissner–Nordström–deSitter spacetime

  Classical and Quantum Gravity · 2020 · 99 citations

  In classical general relativity, the values of elds on spacetime are uniquely determined by their values at an initial time within the domain of dependence of this initial data surface. However, it may occur that the spacetime under consideration extends beyond this domain of dependence, and elds, therefore, are not entirely determined by their initial data. This occurs, for example, in the well-known (maximally) extended Reissner–Nordström or Reissner–Nordström–deSitter (RNdS) spacetimes. The b…

  DOI

• Infrared Finite Scattering Theory in Quantum Field Theory and Quantum Gravity

  arXiv (Cornell University) · 2022-03-27 · 55 citations

  articleOpen accessSenior author

  Infrared (IR) divergences arise in scattering theory with massless fields and are manifestations of the memory effect. There is nothing singular about states with memory, but they do not lie in the standard Fock space. IR divergences are artifacts of trying to represent states with memory in the standard Fock space. For collider physics, one can impose an IR cutoff and calculate inclusive quantities. But, this approach cannot treat memory as a quantum observable and is highly unsatisfactory if o…

  PublisherOA PDFDOI

Recent grants

• Research in Gravitional Physics

  NSF · $660k · 2012–2016

• Research in Gravitational Physics

  NSF · $677k · 2006–2010

• Research in Gravitational Physics

  NSF · $562k · 2018–2021

Frequent coauthors

• Stefan Hollands

  55 shared

• Gautam Satishchandran

  37 shared

• Samuel E. Gralla

  29 shared

• W. G. Unruh

  22 shared

• Alexander Tolish

  Fermi National Accelerator Laboratory

  20 shared

• Daine L. Danielson

  19 shared

• Joshua Schiffrin

  University of Cambridge

  19 shared

• D. E. Holz

  University of Chicago

  19 shared

Awards & honors

• 2025 Dirac Medal
• 2025 Albert Einstein Medal

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• David Awschalomh-116
• Carlos Wagnerh-101