paper

Emergent/Quantum Gravity: Macro/Micro Structures of Spacetime

arXiv:0903.0878 · doi:10.1088/1742-6596/174/1/012015

Abstract

Emergent gravity views spacetime as an entity emergent from a more complete theory of interacting fundamental constituents valid at much finer resolution or higher energies, usually assumed to be above the Planck energy. In this view general relativity is an effective theory valid only at long wavelengths and low energies. For any presumed known theory for the microscopic structure of spacetime, we describe common tasks of emergent gravity (`top-down'), namely, identifying the conditions and processes or mechanisms whereby the familiar macroscopic spacetime emerges with high probability and reasonable robustness. Going in the opposite direction (`bottom-up') is the task of quantum gravity, i.e., finding a theory for the microscopic structure of spacetime, which, in this new view, cannot come from quantizing the metric or connection forms because they are the collective variables which are meaningful only for the macroscopic theory, i.e., general relativity. We suggest pathways to move `up' (in energy) from the given macroscopic conditions of classical gravity and quantum field theory to the domain closer to the micro-macro interface where spacetime emerged and places to look for clues or tell-tale signs at low energy where one could infer indirectly some salient features of the micro-structure of spacetime.

15 pages. Essay for invited talks at the Symposium on "Foundations of Physics", University of Maryland, April 24-27, 2008, Workshop on "Emergent Gravity", MIT, August 25-29, 2008. In Proceedings of DICE 08 Conference, J. Phys. Conf. Ser. (2009)

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