Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Massive Compact Halo Objects from the Relics of the Cosmic Quark-Hadron
  Transition   The existence of compact gravitational lenses, with masses around 0.5
(M_{\odot}), has been reported in the halo of the Milky Way. The nature of
these dark lenses is as yet obscure, particularly because these objects have
masses well above the threshold for nuclear fusion. In this work, we show that
they find a natural explanation as being the evolutionary product of the
metastable false vacuum domains (the so-called strange quark nuggets) formed in
a first order cosmic quark-hadron transition.

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The categories of this paper are: alg-geom
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The categories of this paper are: atom-ph
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The categories of this paper are: math-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: stat
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The categories of this paper are: mtrl-th
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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: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-th
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The categories of this paper are: cs
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The categories of this paper are: nucl-ex
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ex