Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Flow Solutions of Transport Equations   Under general assumptions on the velocity field, it is possible to construct
a flow that is forward untangled. Once such a flow has been selected, the
associated transport problem is well-posed.

34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat