Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the relation between mass of pion, fundamental physical constants and
  cosmological parameters   In this article we reconsider the old mysterious relation, advocated by Dirac
and Weinberg, between the mass of the pion, the fundamental physical constants,
and the Hubble parameter. By introducing the cosmological density parameters,
we show how the corresponding equation may be written in a form that is
invariant with respect to the expansion of the Universe and without invoking a
varying gravitational "constant", as was originaly proposed by Dirac. It is
suggest that, through this relation, Nature gives a hint that virtual pions
dominante the "content" of the quantum vacuum.

28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
1
The categories of this paper are: cs
26
The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th