Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Note on a Non Linear Perturbation of the Ideal Bose Gas   In this work we show that the introduction of a U(1) symmetry breaking field
in the energy operator of the boson-free gas, is equivalent, in the
thermodynamic limit, to the inclusion, in the Hamiltonian of the ideal gas, of
a non-linear function of the number operator associated with the zero mode. In
other words, the limit pressures coincide. Moreover, both models undergo non
conventional Bose-Einstein condensation (BEC) for strictly negative values of
the chemical potential $\mu.$ Finally, the proof of equivalence of limit
pressures is extended to a class of full-diagonal models.

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The categories of this paper are: atom-ph
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The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: eess
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
3
The categories of this paper are: physics
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The categories of this paper are: comp-gas
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The categories of this paper are: q-alg
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The categories of this paper are: supr-con
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The categories of this paper are: q-fin
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The categories of this paper are: plasm-ph