Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A small non-vanishing cosmological constant from the Krein-Gupta-Bleuler
  vacuum   We point out a potential relevance between the Krein-Gupta-Bleuler (KGB)
vacuum leading to a fully covariant quantum field theory for gravity in de
Sitter (dS) spacetime and the observable smallness of the cosmological
constant. This may provide a formulation of linear quantum gravity in a
framework amenable to developing a more complete theory determining the value
of the cosmological constant.

8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
15
The categories of this paper are: nucl-ex