Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the origin of the cosmological constant   Under the assumption that the cosmological constant vanishes in the true
ground state with lowest possible energy density, we argue that the observed
small but finite vacuum-like energy density can be explained if we consider a
theory with two or more degenerate perturbative vacua, which are unstable due
to quantum tunneling, and if we still live in one of such states. An example is
given making use of the topological vacua in non-Abelian gauge theories.

20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph