Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultra-high energy cosmic ray propagation in the Universe   This paper summarizes recent developments in the study of the propagation of
ultra-high energy cosmic ray protons or nuclei in the Universe, with emphasis
on the consequences of energy losses and on the influence of extra-galactic
magnetic fields.

18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat