Research in General Relativity and Quantum Gravity

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This project concerns quantum gravity---the unification of quantum theory and general relativity. The Principal Investigator's approach to this problem is based on the causal set hypothesis, which asserts that the deep structure of spacetime is granular or ``atomic'' with the atoms (``causal set elements'') organized into an extended ``family tree'', known technically as a locally finite partial order. The project will develop this approach further by advancing the underlying theory, while at the same time applying it to questions like that of the cosmological constant, which recently has been shown to contribute roughly two thirds of the effective energy density of the universe. A primary focus of the project will be on the development of a generalization of the classical sequential growth dynamics, found previously, to the case of a quantum causal set.A solution of this problem is generally expected to tell us about the structure of spacetime on the smallest length scales and, at the same time, to help answer questions about why the cosmos is as it is on the largest scales. The project also leads to a new way of understanding time as the continual birth of new elements of the causal set. The algorithms to be developed and the codes to implement them are not only useful in connection with discrete spacetime processes but also have a more general applicability for combinatorial purposes including uses in information technology. Knowledge obtained in fundamental physics such as that studied in this project also appeals to members of the public at large and contributes towards an educated and technically skilled labor force.