Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear instability of scalar fields on extremal black holes   We prove a new type of finite time blow-up for a class of semilinear wave
equations on extremal black holes. The initial data can be taken to be
arbitrarily close to the trivial data. The first singularity occurs along the
(degenerate) future event horizon. No analogue of this instability occurs for
subextremal black holes or the Minkowski spacetime.

8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an