Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Towards a realistic axion star   In this work we estimate the radius and the mass of a self-gravitating system
made of axions. The quantum axion field satisfies the Klein-Gordon equation in
a curved space-time and the metric components of this space-time are solutions
to the Einstein equations with a source term given by the vacuum expectation
value of the energy-momentum operator constructed from the axion field. As a
first step towards an axion star we consider the up to the sixth term in the
axion potential expansion. We found that axion stars would have masses of the
order of asteroids and radius of the order of few centimeters.

19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math