Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fast Radio Burst Tomography of the Unseen Universe   The discovery of Fast Radio Bursts (FRBs) at cosmological distances has
opened a powerful window on otherwise unseen matter in the Universe. In the
2020s, observations of $>10^{4}$ FRBs will assess the baryon contents and
physical conditions in the hot/diffuse circumgalactic, intracluster, and
intergalactic medium, and test extant compact-object dark matter models.

4
The categories of this paper are: cond-mat
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The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics