Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Relatively complicated? Using models to teach general relativity at
  different levels   This review presents an overview of various kinds of models -- physical,
abstract, mathematical, visual -- that can be used to present the concepts and
applications of Einstein's general theory of relativity at the level of
undergraduate and even high-school teaching. After a general introduction
dealing with various kinds of models and their properties, specific areas of
general relativity are addressed: the elastic sheet model and other models for
the fundamental geometric properties of gravity, models for black holes
including the river model, cosmological models for an expanding universe, and
models for gravitational waves as well as for interferometric gravitational
wave detectors.

24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
33
The categories of this paper are: plasm-ph