Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Universal theories and compactly expandable models   Our aim is to solve a quite old question on the difference between
expandability and compact expandability. Toward this, we further investigate
the logic of countable cofinality.

31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an