Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Formation of photon spheres in boson stars with a nonminimally coupled
  field   A static, spherically symmetric, asymptotically flat spacetime may allow for
circular, closed null-geodesics which are said to belong to a photon sphere. In
the context of gravitational lensing in the strong deflection regime, the
presence of a photon sphere leads to an unbounded angle of deflection of light
(multiple turns) and formation of relativistic images. In this paper, we show
that photon spheres may form in some configurations of boson stars constructed
with a free massive complex scalar field nonminimally coupled to gravity.
Assuming that the boson star is transparent to light, photon spheres would give
raise not only to phenomena in the realm of strong gravitational lensing, but
also to considerably increased photon flux in the central region of the star,
relative to the flux in its surroundings.

3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
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The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th