Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phase Transition in Spherically Symmetric Gravitational Collapse of a
  Massless Scalar Field   Phase transition in spherically symmetric collapse of a massless scalar field
is studied in 4-d Einstein gravity. A class of exact solutions that show the
evolution of a constant incoming energy flux turned on at a point in the past
null infinity are constructed to serve as an explicit example. The recently
discovered phase transition in this system via numerical methods
\cite{choptuik} is manifest; above a threshold value of the incooming energy
flux, a black hole is dynamically formed and below that, the incoming flux is
reflected forward into the future null infinity. The critical exponent is
evaluated and discussed using the solutions.

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The categories of this paper are: econ
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The categories of this paper are: adap-org
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The categories of this paper are: physics
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The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
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The categories of this paper are: astro-ph
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The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph