Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultimate fate of apparent horizons during a binary black hole merger II:
  Horizons weaving back and forth in time   In this second part of a two-part paper, we discuss numerical simulations of
a head-on merger of two non-spinning black holes. We resolve the fate of the
original two apparent horizons by showing that after intersecting, their world
tubes "turn around" and continue backwards in time. Using the method presented
in the first paper to locate these surfaces, we resolve several such world
tubes evolving and connecting through various bifurcations and annihilations.
This also draws a consistent picture of the full merger in terms of apparent
horizons, or more generally, marginally outer trapped surfaces (MOTSs). The
MOTS stability operator provides a natural mechanism to identify MOTSs which
should be thought of as black hole boundaries. These are the two initial ones
and the final remnant. All other MOTSs lie in the interior and are neither
stable nor inner trapped.

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The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
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The categories of this paper are: eess
12
The categories of this paper are: nucl-th
3
The categories of this paper are: physics
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: plasm-ph
2
The categories of this paper are: math
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The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex
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The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph