Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Probes and Tests of Strong-Field Gravity with Observations in the
  Electromagnetic Spectrum   Neutron stars and black holes are the astrophysical systems with the
strongest gravitational fields in the universe. In this article, I review the
prospect of probing with observations of such compact objects some of the most
intriguing General Relativistic predictions in the strong-field regime: the
absence of stable circular orbits near a compact object and the presence of
event horizons around black-hole singularities. I discuss the need for a
theoretical framework within which future experiments will provide detailed,
quantitative tests of gravity theories. Finally, I summarize the constraints
imposed by current observations of neutron stars on potential deviations from
General Relativity.

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The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an