Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Closed formula for the matrix elements of the volume operator in
  canonical quantum gravity   We derive a closed formula for the matrix elements of the volume operator for
canonical Lorentzian quantum gravity in four spacetime dimensions in the
continuum in a spin-network basis. We also display a new technique of
regularization which is state dependent but we are forced to it in order to
maintain diffeomorphism covariance and in that sense it is natural. We arrive
naturally at the expression for the volume operator as defined by Ashtekar and
Lewandowski up to a state independent factor.

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The categories of this paper are: plasm-ph
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The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
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The categories of this paper are: hep-th
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex