Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Universal fluctuations and squeezing in generalized Dicke model near the
  superradiant phase transition   In a view of recent proposals for the realization of anisotropic light-matter
interaction in such platforms as (i) non-stationary or inductively and
capacitively coupled superconducting qubits, (ii) atoms in crossed fields and
(iii) semiconductor heterostructures with spin-orbital interaction, the concept
of generalized Dicke model, where coupling strengths of rotating wave and
counter-rotating wave terms are unequal, has attracted great interest. For this
model, we study photon fluctuations in the critical region of
normal-to-superradiant phase transition when both the temperatures and numbers
of two-level systems are finite. In this case, the superradiant quantum phase
transition is changed to a fluctuational region in the phase diagram that
reveals two types of critical behaviors. These are regimes of Dicke model (with
discrete $\mathbb{Z}_2$ symmetry), and that of (anti-) and Tavis-Cummings
$U(1)$ models. We show that squeezing parameters of photon condensate in these
regimes show distinct temperature scalings. Besides, relative fluctuations of
photon number take universal values. We also find a temperature scales below
which one approaches zero-temperature quantum phase transition where quantum
fluctuations dominate. Our effective theory is provided by a non-Goldstone
functional for condensate mode and by Majorana representation of Pauli
operators. We also discuss Bethe ansatz solution for integrable $U(1)$ limits.

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The categories of this paper are: nucl-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-th
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The categories of this paper are: stat
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The categories of this paper are: acc-phys
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The categories of this paper are: econ
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The categories of this paper are: hep-lat
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The categories of this paper are: funct-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: eess
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The categories of this paper are: bayes-an