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Boundary of a spinfoam

  1. Apr 29, 2015 #1

    naima

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    I read in wikipedia that the boundary of a spinfoam is a spin network.
    Is it true?
    How can we define what is the boundary of a finite connected spinfoam?
    I have the same question for a spin network.
    As in LQG boundaries are of paramount importance, I think that we have to define them.
    Thanks
     
  2. jcsd
  3. Apr 30, 2015 #2

    julian

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    You could look at the book "Covariant Loop Quantum Gravity: An Elementary Introduction to Quantum Gravity and Spinfoam Theory" There is a chapter on classical discretization of GR. You may want to look particularly at section 4.4 where they start with the simple case of 3-spatial dimensions and define the connection between bulk and boundary and establish notation. At the start of chapter 7 they talk about the generalization to 4D spacetime.

    A draft version of the book is quoted as here http://www.cpt.univ-mrs.fr/~rovelli/IntroductionLQG.pdf
     
  4. Apr 30, 2015 #3

    atyy

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    http://arxiv.org/abs/1209.4539
    Holonomy Spin Foam Models: Boundary Hilbert spaces and Time Evolution Operators
    Bianca Dittrich, Frank Hellmann, Wojciech Kaminski

    The notion of a boundary is defined in section 3.1, and the spin network basis for the boundary Hilbert space is given in section 3.2.
     
  5. May 3, 2015 #4

    naima

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  6. May 4, 2015 #5

    naima

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    As i understand it in a spin network a boundary is a minimal set of edges. a bondary js between two vertices
    if there is no path between them which can avoid these edges. Is this correct?
     
  7. May 4, 2015 #6

    marcus

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    Dearly Missed

    Try again, I think it is OK now.
    It takes a couple of minutes to download the complete draft of the book (illustrations etc.) so it is not fast, but it does work.
     
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