Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two Topics concerning Black Holes: Extremality of the Energy, Fractality
  of the Horizon   We treat two aspects of the physics of stationary black holes. First we prove
that the proportionality, d(energy) ~ d(area) for arbitrary perturbations
(``extended first law''), follows directly from an extremality theorem drawn
from earlier work. Second we consider quantum fluctuations in the shape of the
horizon, concluding heuristically that they exhibit a fractal character, with
order lambda fluctuations occurring on all scales lambda below M^{1/3} in
natural units.

1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio