Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Low-Lying Electronic Excitations and Nonlinear Optic Properties of
  Polymers via Symmetrized Density Matrix Renormalization Group Method   A symmetrized Density Matrix Renormalization Group procedure together with
the correction vector approach is shown to be highly accurate for obtaining
dynamic linear and third order polarizabilities of one-dimensional Hubbard and
$U-V$ models. The $U-V$ model is seen to show characteristically different
third harmonic generation response in the CDW and SDW phases. This can be
rationalized from the excitation spectrum of the systems.

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The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc