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Finite entanglement entropy from the zero-point-area of spacetime

  1. Jul 29, 2010 #1

    page 4

    "therefore one does not try to quantize gravity but instead attempts to provide a quantum description of spacetime." In other words, canonical quantum gravity is wrong.

    What quantum description of spacetime lends itself most readily to this entropic-emergent understanding of gravity? Do either leading approach work in this context? In string theory, space is infinitely continuous (result of lorentz invariance), do spin networks carry the right kind of microscopic degree of freedom for this idea to work?


    Finite entanglement entropy from the zero-point-area of spacetime
    Authors: T. Padmanabhan
    (Submitted on 28 Jul 2010)

    Abstract: The calculation of entanglement entropy S of quantum fields in spacetimes with horizon shows that, quite generically, S (a) is proportional to the area A of the horizon and (b) is divergent. I argue that this divergence, which arises even in the case of Rindler horizon in flat spacetime, is yet another indication of a deep connection between horizon thermodynamics and gravitational dynamics. In an emergent perspective of gravity, which accommodates this connection, the fluctuations around the equipartition value in the area elements will lead to a minimal quantum of area, of the order of L_P^2, which will act as a regulator for this divergence. In a particular prescription for incorporating L_P^2 as zero-point-area of spacetime, this does happen and the divergence in entanglement entropy is regularized, leading to S proportional to (A/L_P^2) in Einstein gravity. In more general models of gravity, the surface density of microscopic degrees of freedom is different which leads to a modified regularisation procedure and the possibility that the entanglement entropy - when appropriately regularised - matches the Wald entropy.
    Last edited: Jul 29, 2010
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