Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Theoretical bounds on the tensor-to-scalar ratio in the cosmic microwave
  background   Tensor modes in the cosmic microwave background are one of the most robust
signatures of inflation. We derive theoretical bounds on the tensor fraction,
as a generalization of the well-known Lyth bound. Under reasonable assumptions,
the new bounds are at least two orders of magnitude stronger than the original
one. We comment on a previously derived generalization, the so-called
Efstathiou-Mack relationship. We also derive a new absolute upper bound on
tensors using de Sitter entropy bounds.

16
The categories of this paper are: stat
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con