Zenith Grant Awardee

Dr. Steven B. Giddings

University of California at Santa Barbara

Project Title

Observation & Nonlocality in Quantum Gravitational Physics

Project Summary

The physical property of locality is centrally important; it is for example vital to our existence as independent individuals, and part of explaining why we apparently can't travel faster than light. It is also critical in understanding physics inside a black hole, and the universe's beginning in the big bang. Yet recent developments in physics suggest that locality is not absolute, a proposal that this work will investigate. These include advances in string theory, such as the idea of holography, stating that our three-dimensional reality has an equivalent two-dimensional description. Moreover, Hawking's prediction that black holes evaporate precipitated a paradox in physics. This paradox could be as essential as the classical instability of the atom was in developing quantum mechanics, and suggests non-locality. Exploring these issues involves our role as observers in the quantum system that is the universe, and limitations on corresponding observations also indicates breakdown of locality. Understanding observation and its inherent limitations has direct bearing on puzzles in cosmology, such as its accelerating expansion, generation of the observed microwave background fluctuations, and the possibility that we live in a multiverse. These ideas could serve as guides to advances as conceptually profound as the discovery of quantum mechanics.

Technical Abstract

A fundamental problem in quantum gravity is that of describing local observation. Relational observables have been proposed as an answer, but only reduce to local field theory observables in an approximation. This work will investigate aspects of these observables and the proposal that the limitations are indicative of fundamental limits on physics, and locality itself only emerges in an approximate sense. This proposal is also motivated by the black hole information paradox, whose role in physics may be analogous to the classical instability of matter in motivating quantum mechanics. Possible resolution of the paradox through such nonlocality will be investigated. Nonlocality is also motivated by developments in string theory, and will be further explored in that context (for example in high-energy scattering), as will the role of relational observables. Relational observables and the proposed nonlocality also have a potentially important role in cosmology, in understanding and interpreting inflation, de Sitter space, and the possibility of a multiverse, and our role as observers in the cosmological system. Consideration of these issues could play an important role in formulating a fundamental theory incorporating gravity and quantum principles.