Time-space duality in 2D quantum gravity

Abstract

An important task faced by all approaches of quantum gravity is to incorporate superpositions and quantify quantum uncertainties of spacetime causal relations. We address this task in 2D. By identifying a global $Z_2$ symmetry of 1+1D quantum gravity, we show that gravitational path integral configurations come in equal amplitude pairs with timelike and spacelike relations exchanged. As a consequence, any two points are equally probable to be timelike and spacelike separated in a universe without boundary conditions. In the context of simplicial quantum gravity we identify a local symmetry of the action which shows that even with boundary conditions causal uncertainties are generically present. Depending on the boundary conditions, causal uncertainties can still be large and even maximal.

arXiv commentmatches well published version

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Cited by in corpus (4)

• Complex, Lorentzian, and Euclidean simplicial quantum gravity: numerical methods and physical prospects
• Truly Lorentzian quantum cosmology
• Light ray fluctuations in simplicial quantum gravity
• Light ray fluctuation and lattice refinement of simplicial quantum gravity