My parents, both of whom were scientists, escaped Europe in 1940, and I was born in Massachusetts in 1941. I was an undergraduate at Harvard, where I majored in mathematics. For my graduate studies at UC Berkeley, I switched to theoretical physics. My first six postdoctoral years were spent at Princeton University, and in 1972I moved to Caltech, where I have remained ever since. I retired in 2015, but I still try to keep abreast of what is going on. My training in theoretical particle physics focused on the strong nuclear force. These studies eventually drew me into “string theory,” which arose in the late 1960s. This program encountered difficulties in the mid 1970s, and a better theory of the strong nuclear force (QCD) was developed. However, I continued working on string theory, because Joel Scherk and I realized in 1974 that its problems would be converted to virtues if the goal of the program was changed to the construction of a unified quantum theory containing gravity and all other fundamental forces. As I anticipated at the time, this has been the focus of my research ever since.

Research Interests

String theory still is a strong candidate to provide a complete description of the physical universe at the most fundamental level. However, it is not yet fully formulated, and it is unclear how to connect it to observations. In the effort to make progress there have several breakthroughs in recent decades. One is the realization that for a universe with asymptotically anti de Sitter boundary conditions, which is unrealistic, string theory solutions have a dual "holographic" description as more conventional quantum field theories. This has become an enormous subject, which is sometimes referred to as AdS/CFT. In the last few years there has been significant progress towards extending this approach to the much more realistic case of asymptotically four-dimensional Minkowski spacetime boundary conditions. This is a very exciting project, which I would like to contribute to. Another recent hot topic that looks very promising concerns understanding how the formation and decay of black holes (by Hawking radiation) preserves quantum information. These two topics likely have deep connections. Solving them may point to a deeper understanding of string theory and its connection to reality.

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Section 13: Physics