Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Laser Entropy   The entropy of an ordinary (photon) laser and an atom laser (Bose condensate)
is calculated. In particular, the nonzero entropy of a single mode laser or
maser operating near threshold is obtained. This result is to be compared with
the statement frequently made in the study of the maser heat engine to the
effect that: "because maser radiation is in a pure state, its entropy is zero."
Similarly, the entropy of the ground state of a Bose-Einstein condensate
(a.k.a. the atom laser) is also calculated for the first time. This is to be
compared with the textbook wisdom which holds that: "The condensed particles
... are condensed in momentum space, a set of stationary particles ... having
zero energy and zero entropy."

24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas