Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nariai--Bertotti--Robinson spacetimes as a building material for one-way
  wormholes with horizons, but without singularity   We discuss the problem of wormholes from the viewpoint of gluing together two
Reissner--Nordstr\"om-type universes while putting between them a segment of
the Nariai-type world (in both cases there are also present electromagnetic
fields as well as the cosmological constant). Such a toy wormhole represents an
example of one-way topological communication free from causal paradoxes, though
involving a travel to next spacetime sheet since one has to cross at least a
pair of horizons through which the spacetimes' junction occurs. We also
consider the use of thin shells in these constructions. Such a ``material'' for
wormholes we choose taking into account specific properties of the
Nariai--Bertotti--Robinson spacetimes.

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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: math-ph
33
The categories of this paper are: plasm-ph
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The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: stat
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The categories of this paper are: nlin
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The categories of this paper are: chao-dyn