Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Geometric models of particles - the missing ingredient   Einstein's dream of describing elementary particles as solutions of a
classical field theory is severely limited by our current understanding of
Nature. Quantum theory is inconsistent with any local realistic theory such as
evolving topological structures in space. It is shown that allowing time
reversal as an intrinsic part of the structure of elementary particles allows
general relativity to explain quantum theory in principle. Such structures may
also explain electric charge and spin-half.

6
The categories of this paper are: astro-ph
2
The categories of this paper are: math
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th