Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Acceleration of particles to high energy via gravitational repulsion in
  the Schwarzschild field   Gravitational repulsion is an inherent aspect of the Schwarzschild solution
of the Einstein-Hilbert field equations of general relativity. We show that
this circumstance means that it is possible to gravitationally accelerate
particles to the highest cosmic ray energies.

30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
3
The categories of this paper are: physics