Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On wormholes in spacetimes of embedding class one   An $n$-dimensional Riemannian space is said to be of embedding class $m$ if
$n+m$ is the lowest dimension of the flat space in which the given space can be
embedded. A spherically symmetric spacetime of class two can be reduced to
class one by a suitable transformation of coordinates. Applied to wormholes,
given a well-defined shape function $b=b(r)$, the resulting wormhole has an
event horizon and is therefore nontraversable. On a macroscopic scale, $b(r)$
can be replaced by $m(r)$, the effective mass of a spherical star of radius $r$
with $m(0)=0$, to yield a valid solution. Spacetimes of embedding class one
have been used successfully for modeling compact stellar objects. On a
microscopic scale, one can invoke noncommutative geometry to obtain a charged
nontraversable wormhole, i.e., an Einstein-Rosen bridge, and hence a model for
a charged particle.

29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int