Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Paraelectric-to-ferroelectric crossover and electron dynamics from
  time-dependent Hartree-Fock calculations   In recent years, researchers have discovered various excited states of
electrons having an excited domain with a structural order different from the
original one. We examine a dynamics of electron system and phonon system by
using the time-dependent Hartree-Fock approximation. We examine time evolution
with spin degree of freedom. We found a thermally excited
paraelectric-to-ferroelectric crossover. The metastable state is spin pierls
state. We also examine the Landau expansion of electron system at
quarter-filled.

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The categories of this paper are: physics
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The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
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The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
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The categories of this paper are: adap-org
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The categories of this paper are: stat
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The categories of this paper are: econ
5
The categories of this paper are: gr-qc
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The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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The categories of this paper are: math
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The categories of this paper are: cs