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Minkowski vacuum as superposition of spin networks? (Haggard at PI)

  1. Nov 16, 2013 #1

    marcus

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    I'd like to understand better the connection between Hal Haggard's September ILQGS talk
    http://relativity.phys.lsu.edu/ilqgs/
    http://relativity.phys.lsu.edu/ilqgs/haggard091713.pdf
    http://relativity.phys.lsu.edu/ilqgs/haggard091713.wav
    and the talk he gave at PI two days ago:
    http://pirsa.org/13110049/
    Finite regions, spherical entanglement, and quantum gravity
    Speaker(s): Hal Haggard
    An exciting frontier in physics is to understand the quantum nature of gravitation in finite regions of spacetime. Study of these regions from "below'', that is, by studying the quantum geometry of finite regions emerging from loop gravity and spin networks has recently resulted in a new road to the quantization of volume and to evidence that there is a robust gap in the volume spectrum. In this talk I will complement these results with recent work on conformal field theories in a particular finite region, a spherical ball of space. This new view afforded from "above" gives insights into entanglement and the Reeh-Schlieder theorem, allows calculation of the entanglement spectrum, and suggests a new route to constructing the Minkowski vacuum out of independent finite regions in quantum gravity.

    The September talk posed this question:
    "Can we choreograph entanglement to yield the Minkowski vacuum?"
    and for future research suggested:
    "Looking to engineer the Minkowski vacuum and its entanglement from spin network superposition."
     
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  3. Nov 16, 2013 #2

    marcus

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    I want to draw an analogy with a method I've heard of being used in CONDENSED MATTER physics, where you describe the structure of quantum ground states using entanglement in place of energy.

    As I (dimly) understand it (please correct misconceptions) the idea is to use entanglement, rather than energy, in approximating a quantum ground state. For example if you are performing renormalization, then instead of minimizing the energy at each step you choose states that are the "least entangled" with the exterior of a finite region being studied. Thus the renormalization scheme is guided by the reduced density matrix.

    I don't have links to references, so anyone who has is invited to share them. There may even be one or more relevant wikipedia articles.

    It seems to me that Haggard is working on a project to carry over into quantum gravity something that is known to work successfully in condensed matter, and it might turn out to be quite interesting. Incidentally there was a reference in at least one of these talks to Marolf's recent paper about "Holography without strings" (which as I recall also referred to using very ordinary finite regions--for simplicity Haggard is just using a spherical region).
     
  4. Nov 16, 2013 #3

    marcus

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    I should have mentioned, H.H. is reporting work in collaboration with Eugenio Bianchi in both these talks.
     
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