Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Normal modes. The true story   The aim of this article is a comprehensive description of normal modes of
molecular vibrations. The starting point is chosen to be a general molecular
system with separated center of mass and an arbitrary embedding of body-fixed
axes. This allows to focus on internal degrees of freedom only, leaving the
problem of rotational motion behind. Nevertheless, for the sake of completeness
we first introduce a general quantum-mechanical Hamiltonian in Eckart-Watson
representation, to make a quick leap into a simplified harmonic description for
internal motion and rigid rotor for rotational degrees of freedom. This regime
constitutes a basis for more sophisticated calculations.

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The categories of this paper are: math
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
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The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th