Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lifting up the proof theory to the countables : Zermelo-Fraenkel set
  theory   We describe the countable ordinals in terms of iterations of Mostowski
collapsings. This gives a proof-theoretic bound of definable countable ordinals
in the Zermelo-Fraenkel's set theory ZF.

16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con