Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Virtual gravitational dipoles: The key for the understanding of the
  Universe?   Before the end of this decade, three competing experiments (ALPHA, AEGIS and
GBAR) will discover if atoms of antihydrogen fall up or down. We wonder what
the major changes in astrophysics and cosmology would be if it is
experimentally confirmed that antimatter falls upwards. The key point is: If
antiparticles have negative gravitational charge, the quantum vacuum, well
established in the Standard Model of Particles and Fields, contains virtual
gravitational dipoles. The main conclusions are: (1) the physical vacuum
enriched with gravitational dipoles is compatible with a cyclic universe
alternatively dominated by matter and antimatter, without initial singularity
and without need for cosmic inflation; (2) the virtual dipoles might explain
the phenomena usually attributed to dark matter and dark energy. While what we
have presented is still far from a complete theory, hopefully it can stimulate
a radically different and potentially important way of thinking.

5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex