Ph.D. California Institute of Technology, 1974 A.B. (Summa cum laude) Harvard, 1966

Talks by Rafael Sorkin

A possible causality-condition for causal sets: persistence of zero

Rafael Sorkin Perimeter Institute for Theoretical Physics
Within a histories-framework for quantum field theory, the condition of \bold{persistence of zero} (PoZ for short) tries to capture (a part of) the elusive idea that no cause can act outside its future lightcone. The PoZ condition, however, does not easily carry over to theories like gravity where the causal structure is not only dynamical but indefinite (subject to quantum fluctuations).

The Quantum Measure -- And How To Measure It

Rafael Sorkin Perimeter Institute for Theoretical Physics

When utilized appropriately, the path-integral offers an alternative to the ordinary quantum formalism of state-vectors, selfadjoint operators, and external observers -- an alternative that seems closer to the underlying reality and more in tune with quantum gravity. The basic dynamical relationships are then expressed, not by a propagator, but by the quantum measure, a set-function $\mu$ that assigns to every (suitably regular) set $E$ of histories its generalized measure $\mu(E)$.

Projective Statistics in Quantum Gravity

Rafael Sorkin Perimeter Institute for Theoretical Physics
To the extent that spacetime remains a manifold M on small scales, excitations of the spatial topology can function as particles called topological geons. In a first quantized theory of topological geons (aka continuum quantum gravity without topology change), different irreducible unitary representations of the mapping-class group G of M, yield different superselection sectors of the theory. In some of these sectors the geons behave as fermions, even though gravitons themselves are of course bosons.