Quantum field theory with classical sources—linearized quantum gravity

Quantum Gravity as Topological Quantum Field Theory

The physics of quantum gravity is discussed within the framework of topological quantum field theory. Some of the principles are illustrated with examples taken from theories in which space-time is three dimensional.

DISCRETE QUANTUM GRAVITY and QUANTUM FIELD THEORY

We introduce a discrete 4-dimensional module over the integers that appears to have maximal symmetry. By adjoining the usual Minkowski distance, we obtain a discrete 4-dimensional Minkowski space. Forming universe histories in this space and employing the standard causal order, the histories become causal sets. These causal sets increase in size rapidly and describe an inflationary period for t...

From Classical Theory to Quantum Gravity

While it has been generally accepted for decades that general relativity and quantum theory are inconsistent, and that therefore general relativity must yield to a new theory of gravity compatible with quantum principles, the way to the new theory is still very unclear. A major obstacle is the lack of any experimental indicators as to where general relativity might break down. I speculate on th...

Classical and Quantum Gravity

Linking topological quantum field theory and nonperturbative quantum gravity

Quantum gravity is studied nonperturbatively in the case in which space has a boundary with finite area. A natural set of boundary conditions is studied in the Euclidean signature theory, in which the pullback of the curvature to the boundary is self-dual (with a cosmological constant). A Hilbert space which describes all the information accessible by measuring the metric and connection induced...