Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Visible, invisible and trapped ghosts as sources of wormholes and black
  universes   We construct explicit examples of globally regular static, spherically
symmetric solutions in general relativity with scalar and electromagnetic
fields, describing traversable wormholes with flat and AdS asymptotics and
regular black holes, in particular, black universes. (A black universe is a
regular black hole with an expanding, asymptotically isotropic space-time
beyond the horizon.) Such objects exist in the presence of scalar fields with
negative kinetic energy ("phantoms", or "ghosts"), which are not observed under
usual physical conditions. To account for that, we consider what we call
"trapped ghosts" (scalars whose kinetic energy is only negative in a
strong-field region of space-time) and "invisible ghosts", i.e., phantom scalar
fields sufficiently rapidly decaying in the weak-field region. The resulting
configurations contain different numbers of Killing horizons, from zero to
four.

15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th