Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gravitational lens on de-Sitter background   Gravitational lenses are examined in de-Sitter (dS) background, for which the
existence of the dS horizon is taken into account and hyperbolic trigonometry
is used together with the hyperbolic angular diameter distance. Spherical
trigonometry is used to discuss a gravitational lens in anti-de Sitter (AdS)
background. The difference in the form among the dS/AdS lens equations and the
exact lens equation in Minkowski background begins at the third order, when a
small angle approximation is used in terms of lens and source planes. The
angular separation of lensed images is decreased by the third-order deviation
in the dS lens equation, while it is increased in AdS. In the present framework
on the dS/AdS backgrounds, we discuss also the deflection angle of light, which
does not include any term of purely the cosmological constant. Despite the
different geometry, the deflection angle of light rays in hyperbolic and
spherical geometry can take the same form. Through a coupling of the
cosmological constant with lens mass, the separation angle of multiple images
is larger (smaller) in dS (AdS) than in the flat case, for a given mass, source
direction, and angular diameter distances among the lens, receiver and source.

25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin