Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: What if ... General Relativity is not the theory?   The nature of gravity is fundamental to understand the scaffolding of the
Universe and its evolution. Einstein's general theory of relativity has been
scrutinized for over ninety five years and shown to describe accurately all
phenomena from the solar system to the Universe. However, this success is
achieved in the case of the largest scales provided one admits contributions to
energy-momentum tensor involving dark components such as dark energy and dark
matter. Moreover, the theory has well known shortcomings, such as the problem
of singularities, the cosmological constant problem and the well known initial
conditions problems for the cosmological description. Furthermore, general
relativity also does not fit the well known procedures that allow for the
quantization of the other fundamental interactions. In this discussion we
briefly review the experimental bounds on the foundational principles of
general relativity, and present three recent proposals to extend general
relativity or, at least, to regard it under different perspectives.

22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg