Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Density-matrix renormalization group study of optical conductivity of
  the Mott insulator for two-dimensional clusters
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
6
The categories of this paper are: astro-ph
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs