Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: On the necessity of phantom fields for solving the horizon problem in
  scalar cosmologies
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
2
The categories of this paper are: math
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
18
The categories of this paper are: econ
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin