Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sensitivity to perturbations and quantum phase transitions   The local density of states or its Fourier transform, usually called fidelity
amplitude, are important measures of quantum irreversibility due to imperfect
evolution. In this Rapid Communication we study both quantities in a
paradigmatic many body system, the Dicke Hamiltonian, where a single-mode
bosonic field interacts with an ensemble of N two-level atoms. This model
exhibits a quantum phase transition in the thermodynamic limit, while for
finite instances the system undergoes a transition from quasi-integrability to
quantum chaotic. We show that the width of the local density of states clearly
points out the imprints of the transition from integrability to chaos but no
trace remains of the quantum phase transition. The connection with the decay of
the fidelity amplitude is also established.

35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
6
The categories of this paper are: astro-ph