Tai Tsun Wu

Tai Tsun Wu, a distinguished theoretical physicist and professor of physics and applied physics at Harvard University, passed away on 19 July 2024 in Palo Alto, California. He was 90 years old. Wu was known for his groundbreaking research in antenna theory, statistical physics, and perturbative quantum field theory.

Born on 1 December 1933, in Shanghai, China, Tai Tsun Wu came to the US in November 1950 and studied electrical engineering at the University of Minnesota. In 1953, he was a winner of the Putnam mathematical competition. Moving to Harvard, he earned a doctorate in applied physics in 1956 at the age of 22, working with Ronold King. Wu’s graduate work established him as an extraordinary master of antenna theory for electromagnetic waves.

Wu joined the Harvard faculty in 1959. In 1966, he became the Gordon McKay Professor of Applied Physics; in 1994, he was also appointed a professor of physics.

Beginning in the 1960s, Wu carried out a series of tour-de-force calculations on the 2D Ising model in papers with Barry McCoy and Craig Tracy. Among other results, they computed the spin correlation function for spins at arbitrary orientation relative to the crystal axes, demonstrating explicitly how the rotationally invariant scaling theory sets in as one approaches the critical point. They discovered that the scaling functions are given in terms of Painlevé transcendental functions, opening a new line of mathematical research on integrable systems.

In a long collaboration with Hung Cheng at MIT, Wu investigated the high-energy behavior of elementary particle scattering cross sections by explicit summation of large classes of Feynman diagrams in scalar field theory and quantum electrodynamics. The results predicted the rise of the proton–proton total cross section observed in the early 1970s at the CERN Intersecting Storage Rings and were instrumental in interpreting the phenomena of diffraction scattering and multiple hadron production observed at CERN, including at the LHC.

In a series of papers with C. N. Yang in 1975–76, Wu reformulated the mathematical treatment of magnetic monopoles. Using ideas from differential geometry and the theory of fiber bundles, Wu and Yang represented the wavefunctions of particles moving in the field of a magnetic monopole in terms of “monopole harmonics,” generalizing the usual spherical harmonics. These monopole harmonics are smooth in their appropriate coordinate patches and are linked across patches by gauge transformations. This formulation replaced the singular “Dirac strings” previously used to describe monopoles. These harmonics and their generalizations have become an essential tool for the study of monopoles and topological gauge field configurations in higher dimensions. Mathematicians have formulated these ideas as the “Wu–Yang dictionary” linking concepts in physics and differential geometry.

In his final years, Wu contributed to the theory of the Higgs boson. He pursued the idea that the standard model implies additional relations between the masses of its heaviest particles (W, Z, H, and t) that are not obvious from the Lagrangian and that give insight into the Higgs phenomenon. His last published work at the age of 89, “Concept of the basic standard model and a relation between the three gauge coupling constants,” was published in 2023.

In recognition of his contributions, Wu received a number of honors and prizes, including the Dannie Heineman Prize for Mathematical Physics of the American Institute of Physics and the American Physical Society (1999) and the Alexander von Humboldt Prize (1985–86). He was a fellow of the American Academy of Arts and Sciences and a member of the Academia Sinica in Taiwan. Wu wrote more than 400 original papers and 6 books. Noteworthy among the books are The Scattering and Diffraction of Waves (1959), with R. W. P. King; The Two-Dimensional Ising Model (1973), with B. McCoy; and Expanding Protons: Scattering at High Energies (1987), with H. Cheng.

Wu was not only a brilliant scientist but also a dedicated mentor and an inspiration to young scientists. He spent significant time in collaborations at CERN, DESY, Utrecht University, the University of Bergen, the Institute for Advanced Study in Princeton, and Rockefeller University.

Wu is survived by his wife Sau Lan Wu, with whom he shared a life of intellectual and personal partnership. Tai met Sau Lan when she was a graduate student in the Harvard physics department. Sau Lan went on to become a prominent figure in experimental particle physics. She held the position of Enrico Fermi Professor at the University of Wisconsin and played a central role in the discoveries of the J/ψ particle, the gluon, and the Higgs boson. The couple was known for their close collaboration, which brought Tai Tsun Wu’s theoretical insight to these experimental advances.

Tai Tsun Wu’s passing is a profound loss to the scientific community and all who knew him. We hope that his legacy will continue to inspire future generations of physicists. May his memory be a source of inspiration and his contributions a guiding light for many years to come.

Obituaries are made available as a service to the physical sciences community and are not commissioned by Physics Today. Submissions are lightly edited for grammar and style. Click here for guidelines on submitting an obituary. If you are a copyright holder who thinks that an obituary violates your copyright, please contact us .