Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Filling of a cavity with zero-point electromagnetic radiation   In the present contribution we analyse a simple thought process at T = 0 in
an idealized heat engine having partitions made of a material with an upper
frequency cut-off and bathed in zero-point (ZP) electromagnetic radiation. As a
result, a possible mechanism of filling real cavities with ZP radiation based
on Doppler's effect has been suggested and corresponding entropy changes are
discussed.

2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex