Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the inverse problem of finding cosmic strings and other topological
  defects   We consider how microlocal methods developed for tomographic problems can be
used to detect singularities of the Lorentzian metric of the Universe using
measurements of the Cosmic Microwave Background radiation. The physical model
we study is mathematically rigorous but highly idealized.

28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
3
The categories of this paper are: physics
13
The categories of this paper are: quant-ph
22
The categories of this paper are: chao-dyn