Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Clustering in the X-ray Universe   In this paper we discuss various possibilities of using X-ray observations to
gain information about the large-scale structure of the Universe. After
reviewing briefly the current status of these investigations we explore
different ways of making progress in this field, using deep surveys, large area
surveys and X-ray background observations.

2
The categories of this paper are: math
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
4
The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics