Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Collapse and revival of ultracold atoms in a microwave cavity and of
  photons in parametric down-conversion   We present a new theoretical method to study a trapped gas of bosonic
two-level atoms interacting with a single mode of a microwave cavity. This
interaction is described by a trilinear Hamiltonian which is formally
completely equivalent to the one describing parametric down-conversion in
quantum optics. A system of differential equations describing the evolution,
including the long-time behaviour, of not only the mean value but also the
variance of the number of excited atoms is derived and solved analytically. For
different initial states the mean number of excited atoms exhibits periodically
reappearing dips, with an accompanying peak in the variance, or fractional
collapses and revivals. Closed expressions for the period and the revival time
are obtained.

35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
29
The categories of this paper are: funct-an