Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Horizons in matter: black hole hair vs. Null Big Bang   It is shown that only particular kinds of matter (in terms of the "radial"
pressure to density ratio $w$) can coexist with Killing horizons in black-hole
or cosmological space-times. Thus, for arbitrary (not necessarily spherically
symmetric) static black holes, admissible are vacuum matter ($w=-1$, i.e., the
cosmological constant or some its generalization) and matter with certain
values of $w$ between 0 and -1, in particular, a gas of disordered cosmic
strings ($w=-1/3$). If the cosmological evolution starts from a horizon (the
so-called Null Big Bang scenarios), this horizon can co-exist with vacuum
matter and certain kinds of phantom matter with $w\geq -3$. It is concluded
that normal matter in such scenarios is entirely created from vacuum.

24
The categories of this paper are: dg-ga
13
The categories of this paper are: quant-ph
21
The categories of this paper are: adap-org
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
17
The categories of this paper are: q-fin