Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Remarks on the Entropy of Non-Stationary Black Holes   The definition of entropy obtained for stationary black holes is extended in
this paper to the case of non-stationary black holes. Entropy is defined as a
macroscopical thermodynamical quantity which satisfies the first principle of
thermodynamics. In the non-stationary case a volume term appears since the
solution does not admit a Killing vector.

13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
12
The categories of this paper are: nucl-th
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an