New views on the low-energy side of gravity

Abstract

Common wisdom associates all the unraveled and theoretically challenging aspects of gravity with its UV-completion. However, there appear to be few difficulties afflicting the effective framework for gravity already at low energy, that are likely to be detached from the high-energy structure. Those include the black hole information paradox, the cosmological constant problem and the rather involved and fine tuned model building required to explain our cosmological observations. I review some on-going research that aims to generalize and extend the low-energy framework for gravity. In a quantum informational fashion, regions of space at a given time are treated and described as quantum subsystems, rather than submanifolds. The idea is to define a region of space through the quantum degrees of freedom of the matter fields "living therein". I show how the correspondence sub-system/sub-manifold is realized in standard semi-classical gravity ("standard localization") and discuss the implications of alternative localization schemes. By exploiting further the subsystem description, I then consider the possibility that the usual GR metric manifold description might break down in the infra-red. This has implications on the description of the Universe on the largest scales and on dark energy.

Review based on talks given at DICE (Castiglioncello) 2008, Emergent gravity III (Boston 2008) and IV (Vancouver 2009), New Prospects for Solving the Cosmological Constant Problem (Perimeter Institute 2009) and several other more or less informal discussions. 51 pages, 2 figures. References added

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Cited by in corpus (6)

• Generalized Uncertainty Principle: Approaches and Applications
• Friedmann Equations from Entropic Force
• Surface Density of Spacetime Degrees of Freedom from Equipartition Law in theories of Gravity
• Entropic Law of Force, Emergent Gravity and the Uncertainty Principle
• Gauss-Codazzi thermodynamics on the timelike screen
• Black Hole Motion in Entropic Reformulation of General Relativity