Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: General static black holes in matter   For arbitrary static space-times, it is shown that an equilibrium between a
Killing horizon and matter is only possible for some discrete values of the
parameter $w = p_1/\rho$, where $\rho$ is the density and $p_1$ is pressure in
the direction normal to the horizon. In the generic situation of a simple
(non-extremal) horizon and the slowest possible density decrease near the
horizon, this corresponds to $w = -1/3$, the value known for a gas of
disordered cosmic strings. An admixture of "vacuum matter", characterized by
$w=-1$ and nonzero density at the horizon, is also admitted. This extends the
results obtained previously for static, spherically symmetric space-times. A
new feature as compared to spherical symmetry is that higher-order horizons can
exist in the absence of vacuum matter if the horizon is a surface of zero
curvature, which can occur, e.g., in cylindrically symmetric space-times.

1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
4
The categories of this paper are: cond-mat
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess