Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A detailed exploration of the EDGES 21 cm absorption anomaly and
  axion-induced cooling   The EDGES collaboration's observation of an anomalously strong 21 cm
absorption feature around the cosmic dawn era has energised the cosmological
community by suggesting a novel signature of dark matter in the cooling of
cosmic hydrogen. In a recent letter we have argued that by virtue of the
ability to mediate cooling processes whilst in the condensed phase, a small
amount of axion dark matter can explain these observations within the context
of standard models of axions and axion-like particles. These axions and
axion-like particles (ALPs) can thermalize through gravitational
self-interactions and so eventually form a Bose-Einstein condensate (BEC),
whereupon large-scale long-range correlation can produce experimentally
observable signals such as these. In this context the EDGES best-fit result
favours an axion-like-particle mass in the (6, 400) meV range. Future
experiments and galaxy surveys, particularly the International Axion
Observatory (IAXO) and EUCLID, should have the capability to directly test this
scenario. In this paper, we will explore this mechanism in detail and give more
thorough computational details of certain key points.

15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an