Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Almost Parallel Structures   A discussion of torsion of Riemannian G-structures leads to a survey of
contributions of Alfred Gray and others on almost Hermitian manifolds,
G_2-manifolds, curvature identities, volume expansions, plotting geodesics, and
the geometry of nilmanifolds. The paper concludes with a new example of a
compact 8-manifold with a quaternionic 4-form that is closed but not parallel.

31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
7
The categories of this paper are: hep-th