Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Families of regular matroids   This is an introductory paper about the category of regular oriented matroids
(ROMs). We compare the homotopy types of the categories of regular and binary
matroids. For example, in the unoriented case, they have the same fundamental
group but we show that the higher homotopy groups are different for rank three
regular and binary matroids. We also speculate on the possible impact of a
recent theorem of Galatius [Gal] computing the stable cohomology of the
category of graphs and on possible applications to higher Reidemeister torsion.

36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ