Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An extension of Birkhoff's theorem to a class of 2-d gravity theories
  containing black holes   A class of 2-dimensional models including 2-d dilaton gravity, spherically
symmetric reduction of d-dimensional Einstein gravity and other related
theories are classically analyzed. The general analytic solutions in the
absence of matter fields other than a U(1) gauge field are obtained under a new
gauge choice and recast in the conventional conformal gauge. These solutions
imply that Birkhoff's theorem, originally applied to spherically symmetric 4-d
Einstein gravity, can be applied to all models we consider. Some issues related
to the coupling of massless scalar fields and the quantization are briefly
discussed.

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The categories of this paper are: cond-mat
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The categories of this paper are: eess
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The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom
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The categories of this paper are: q-bio
18
The categories of this paper are: econ
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The categories of this paper are: stat
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The categories of this paper are: physics
34
The categories of this paper are: chem-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
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The categories of this paper are: astro-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
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The categories of this paper are: hep-lat