Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Early evolution of the Galactic halo revealed from Hipparcos
  observations of metal-poor stars
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex