Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phase structure of the QCD vacuum in a magnetic field at low temperature   We study the QCD phase structure in magnetic field $H$ at low temperature
$T$. The hadronic phase free energy in a constant homogeneous magnetic field is
calculated in one-loop approximation of the chiral perturbation theory. The
dependence of the quark and gluon condensates upon the temperature and field
strength is found. It is shown that the chiral phase transition order parameter
$<\bar q q>$ remains constant provided field strength and temperature are
related via $H=const \cdot T^2$.

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The categories of this paper are: chao-dyn
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The categories of this paper are: atom-ph
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The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
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The categories of this paper are: solv-int
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The categories of this paper are: quant-ph
1
The categories of this paper are: cs
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The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math