Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Improved constraints on dark energy from Chandra X-ray observations of
  the largest relaxed galaxy clusters
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
16
The categories of this paper are: stat
11
The categories of this paper are: hep-lat
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci