Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: General theory of cosmological perturbations in open and closed
  universes from the Horndeski action   Our Universe is nearly spatially flat, but this does not mean that it is
exactly spatially flat. In this paper we derive general quadratic actions for
cosmological perturbations in non-flat models from the Horndeski theory. This
allows us to study how the spatial curvature influences the behavior of
cosmological perturbations in the early universe described by some general
scalar-tensor theory. We show that a tiny spatial curvature at the onset of
inflation is unlikely to yield large (or ${\cal O}(1)$) effects on the
primordial spectra even if one modifies gravity. We also argue that
non-singular cosmological solutions in the Horndeski theory are unstable in
spatially open cases as well as in flat cases.

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The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
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The categories of this paper are: eess
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex