Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gravitational Waves and Black Holes: an Introduction to General
  Relativity   In these lectures general relativity is outlined as the classical field
theory of gravity, emphasizing physical phenomena rather than mathematical
formalism. Dynamical solutions representing traveling waves as well as
stationary fields like those of black holes are discussed. Their properties are
investigated by studying the geodesic structure of the corresponding
space-times, as representing the motion of point-like test particles. The
interaction between gravitational, electro-magnetic and scalar fields is also
considered.

7
The categories of this paper are: hep-th
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int