Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A note on Penrose's Spin-Geometry Theorem and the geometry of `empirical
  quantum angles'   In the traditional formalism of quantum mechanics, a simple direct proof of
(a version of) the Spin Geometry Theorem of Penrose is given; and the structure
of a model of the `space of the quantum directions', defined in terms of
elementary $SU(2)$-invariant observables of the quantum mechanical systems, is
sketched.

30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
21
The categories of this paper are: adap-org