Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Improving the Efficiency of an Ideal Heat Engine: The Quantum
  Afterburner   By using a laser and maser in tandem, it is possible to obtain laser action
in the hot exhaust gases involved in heat engine operation. Such a "quantum
afterburner" involves the internal quantum states of working gas atoms or
molecules as well as the techniques of cavity quantum electrodynamics and is
therefore in the domain of quantum thermodynamics. As an example, it is shown
that Otto cycle engine performance can be improved beyond that of the "ideal"
Otto heat engine.

8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol