Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: The evolution of radiation towards thermal equilibrium: A soluble model
  which illustrates the foundations of Statistical Mechanics
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an