Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Euler-Poincar\'e obstruction for pretzels with long tentacles \`a la
  Cantor-Nyikos   We present an avatar of the Euler obstruction to foliated structures on
certain non-metric surfaces. This adumbrates (at least for the simplest
2D-configurations) that the standard mechanism---to the effect that the devil
of algebra sometimes barricades the existence of angelic geometric structures
(obstruction theory more-or-less)---propagates slightly beyond the usual
metrical proviso. Alas, the game is much more conservative than revolutionary:
in particular we enjoyed retrospecting at Poincar\'e's argument of 1885
(announced in 1881).

1
The categories of this paper are: cs
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
3
The categories of this paper are: physics
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org