We review the consistent histories formulations of quantum mechanics developed by Griffiths, Omnès and Gell-Mann and Hartle, and describe the classification of consistent sets. We illustrate some… (More)

A one parameter family of retarded linear operators on scalar fields on causal sets is introduced. When the causal set is well approximated by 4 dimensional Minkowski spacetime, the operators are… (More)

The result that, for a scalar quantum field propagating on a “trousers” topology in 1 + 1 dimensions, the crotch singularity is a source for an infinite burst of energy has been used to argue against… (More)

One obtains Bell’s inequalities if one posits a hypothetical joint probability distribution, or measure, whose marginals yield the probabilities produced by the spin measurements in question. The… (More)

We present spontaneous collapse models of field theories on a 1 + 1 null lattice, in which the causal structure of the lattice plays a central role. Issues such as " locality, " " non-locality " and… (More)

An expression for the spacetime absorption coefficient of a scalar field in a five dimensional, near extremal black hole background is derived, which has the same form as that presented by Maldacena… (More)

The structure of Collapse Models is investigated in the framework of Quantum Measure Theory, a histories-based approach to quantum mechanics. The underlying structure of coupled classical and quantum… (More)

The causal set approach to quantum gravity embodies the concepts of causal-ity and discreteness. This article explores some foundational and conceptual issues within causal set theory.

A particular approach to topology change in quantum gravity is reviewed, showing that several aspects of Stephen's work are intertwined with it in an essential way. Speculations are made on possible… (More)