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Zenith Grant Awardee

Joseph Polchinski

University of California, Santa Barbara


Project Title

Gauge/Gravity Duality and the Emergence of Time and Space

Project Summary

Black holes are remarkable objects, and they provide a rich theoretical laboratory for studying the unification of quantum mechanics and gravity. In fact, they point to a conflict, leading Hawking and others to conclude that there must be radical changes either to quantum theory or to our understanding of spacetime. Recent developments from string theory point to the latter: spacetime as we perceive it is not fundamental, but emerges `holographically' from a theory in fewer dimensions. Ultimately this will greatly change the way we think about space and time, and about the structure of the universe and its beginning, but building a theory based on such an unfamiliar and counterintuitive starting point is a great challenge. Fortunately we have one precise mathematical model, the so-called AdS/CFT duality, that works in special kind of spacetime. Further, this model reveals an unexpected connection between gravity and the other forces. We propose to understand this example and build on it, through the construction of simplified models of black holes and expanding universes, and the application of various powerful tools and organizing principles that have been developed for the other forces.

Technical Abstract

The paradoxes of black hole quantum mechanics led 't Hooft and Susskind to propose the holographic principle, that quantum gravity in any space should be formulated in terms of fundamental degrees of freedom on its boundary. AdS/CFT duality has confirmed this remarkable insight, for spaces with special boundaries. The holographic principle is thus likely to be central to the ultimate understanding of space, time, and quantum gravity. Extending this to general spaces, especially to spaces with interesting cosmologies where there is no natural boundary, is the key challenge. We propose to address this through several approaches, including (1) developing the parallel between the Wilson renormalization group in the boundary theory and the holographic renormalization group in the bulk so as to develop a more local notion of holography; (2) extending our earlier work on sufficient conditions for field theories to give rise to emergent spacetimes; (3) continued study of the black hole paradoxes, through simplified models of the AdS/CFT duality; (4) precise characterizations of the distinction between holographic and nonholographic theories, so as to clarify the nature of holography; and (5) studies of holography in supercritical string backgrounds.

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