Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Variations of gwistor space   We study natural variations of the G2 structure {\sigma}_0 \in {\Lambda}^3_+
existing on the unit tangent sphere bundle SM of any oriented Riemannian
4-manifold M. We find a circle of structures for which the induced metric is
the usual one, the so-called Sasaki metric, and prove how the original
structure has a preferred role in the theory. We deduce the equations of
calibration and cocalibration, as well as those of W3 pure type and
nearly-parallel type.

19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
3
The categories of this paper are: physics
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex