Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The First Sources of Light in the Universe   The formation of the first stars and quasars marks the transition between the
smooth initial state and the clumpy current state of the Universe. In popular
CDM cosmologies, the first sources of light started to form at a redshift z=30
and ionized most of the hydrogen in the Universe by z=8. Current observations
are at the threshold of probing the reionization epoch. The study of
high-redshift sources is likely to attract major attention in observational and
theoretical cosmology over the next decade.

29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph