Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A stably free nonfree module and its relevance for homotopy
  classification, case Q_{28}   The paper constructs an `exotic' algebraic 2-complex over the generalized
quaternion group of order 28, with the boundary maps given by explicit matrices
over the group ring. This result depends on showing that a certain ideal of the
group ring is stably free but not free. As it is not known whether the complex
constructed here is geometrically realizable, this example is proposed as a
suitable test object in the investigation of an open problem of C.T.C. Wall,
now referred to as the D(2)-problem.

23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
18
The categories of this paper are: econ
15
The categories of this paper are: nucl-ex
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys