Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A solution to the Baer splitting problem   Let R be a commutative domain. We prove that an R-module B is projective if
and only if Ext^1(B,T)=0 for any torsion module T. This answers in the
affirmative a question raised by Kaplansky in 1962.

1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph