version 1.2 Symmetry-breaking and zero-one laws Fay Dowker Perimeter Institute, 31 Caroline Street North, Waterloo ON, N2L 2Y5 Canada and Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2AZ, UK address for email:
[email protected] and Rafael D. Sorkin Perimeter Institute, 31 Caroline Street North, Waterloo ON, N2L 2Y5 Canada and Raman Research Institute, C.V. Raman Avenue, Sadashivanagar, Bangalore { 560 080 India and Department of Physics, Syracuse University, Syracuse, NY 13244-1130, U.S.A. address for email:
[email protected] Abstract We offer further evidence that discreteness of the sort inherent in a causal set cannot, in and of itself, serve to break Poincar´einvariance. In par- ticular we prove that a Poisson sprinkling of Minkowski spacetime can- not endow spacetime with a distinguished spatial or temporal orienta- tion, or with a distinguished lattice of spacetime points, or with a distin- guished lattice of timelike directions (corresponding respectively to break- ings of reflection-invariance, translation-invariance, and Lorentz invari- ance). Along the way we provide a proof from first principles of the zero- one law on which our new arguments are based. Keywords and phrases: discreteness, symmetry breaking, zero-one law, Poisson process, causal set, quantum gravity Introduction Will a discrete structure prove to be the kinematical basis of quantum gravity and if so should we expect it to preserve the known symmetries of Minkowski spacetime, at 1 least quasi-locally? One strand of thought has tended to answer these questions with \yes" followed by \no", and has held out effects like modified dispersion relations for electromagnetic waves as promising candidates for a phenomenology of spatiotemporal discreteness.