Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Flows in Flatland: A Romance of Few Dimensions   In this paper, we present our general results about traversing flows on
manifolds with boundary in the context of the flows on surfaces with boundary.
We take advantage of the relative simplicity of $2D$-worlds to explain and
popularize our approach to the Morse theory on smooth manifolds with boundary,
in which the boundary effects take the central stage.

21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc