Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum phase transitions and thermodynamics of quantum antiferromagnets
  with competing interactions   We study the isotropic Heisenberg chain with nearest and next-nearest
neighbour interactions. The ground state phase diagram is constructed in
dependence on the additonal interactions and an external magnetic field. The
thermodynamics is studied by use of finite sets of non-linear integral
equations resulting from integrabiliy. The equations are solved numerically and
analytically in suitable limiting cases. We find second and first order
transition lines. The exponents of the low temperature asymptotics at the phase
transitions are determined.

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The categories of this paper are: astro-ph
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The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom
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The categories of this paper are: nlin
3
The categories of this paper are: physics
21
The categories of this paper are: adap-org