Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Thermodynamic properties of the XX model in a chain with a period two
  and three coupling   The exact solutions for the energy spectrum of the XX model with a periodic
coupling and an external transverse magnetic field $h$ are obtained. The
diagonalization procedure is discussed, and analytical and numerical solutions
are given. Using the solutions for period-two coupling, the free energy,
entropy, and specific heat are calculated as functions of temperature and
applied transverse external magnetic field. Their expressions show that below a
particular value $v$ and above a value $u$ of the magnetic field $|h|$, the
entropy and the specific heat vanish exponentially in the low temperature
limit.

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The categories of this paper are: funct-an
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
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The categories of this paper are: eess
23
The categories of this paper are: solv-int