Mathematician Horng-Tzer Yau, who has harnessed the power of mathematics to analyze and explain physical processes from atomic behavior to the stability of stars, has been named professor of mathematics in Harvard University’s Faculty of Arts and Sciences, effective July 1.

Yau, 45, comes to Harvard from Stanford University, where he is currently professor of mathematics. Yau was previously on the faculty of New York University’s (NYU) Courant Institute of Mathematical Sciences.

“Professor Yau is a leader in the fields of mathematical physics, analysis, and probability,” says William C. Kirby, Edith and Benjamin Geisinger Professor of History and dean of the Faculty of Arts and Sciences. “He is a powerful analyst who has introduced important tools and concepts to study probability, stochastic processes, nonequilibrium statistical physics, and quantum dynamics. His insight and skilled teaching will be invaluable to our graduate and undergraduate students.”

Yau uses statistical mechanics to interpret descriptive models of physical phenomena on a scale ranging from microscopic to astronomical. He has used quantum mechanics to describe the stability of matter in systems composed of many bodies, yielding mathematical support for earlier astrophysical theories on the limits of stellar stability.

Yau’s studies have also helped explain the macroscopic properties of fluids based on their atomic behavior. He pioneered the concept of “relative entropy” to derive descriptive formulae of fluid behavior – such as the Euler and Navier-Stokes equations of classical fluid mechanics – from basic principles of statistical mechanics. He has also recently proved that Brownian motion emerges from a quantum particle in a random environment, a question pondered decades ago by Albert Einstein as he studied the Brownian motion of classical particles in a random environment.

Beyond these additions to our understanding of physical phenomena, Yau has also made important fundamental contributions in probability theory, nonlinear partial differential equations, spectral theory, and dynamical systems theory.

A native of Taiwan, Yau received a B.Sc. from National Taiwan University in 1981 and a Ph.D. from Princeton University in 1987. He joined NYU in 1988, becoming a full professor in 1994, and became professor of mathematics at Stanford in 2003. He has served as a member of the Institute for Advanced Study in Princeton, N.J., in 1987-88, 1991-92, and 2003.

Honors accorded Yau include a Sloan Foundation Fellowship and Packard Foundation Fellowship, both in 1991, and the Henri Poincare Prize and a MacArthur Fellowship, commonly referred to as the “genius grant,” in 2000. A member of the American Academy of Arts and Sciences, Yau has served on the editorial boards of the journals Communications in Mathematical Physics, Journal of Statistical Mathematics, Asian Journal of Mathematics, and Communications in Pure and Applied Mathematics.