Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Notes on Local Grand Unification   Grand unified models in four dimensions typically suffer from the
doublet-triplet splitting problem. This obstacle can be overcome in
higher-dimensional settings, where a non-trivial gauge group topography can
explain the simultaneous appearance of complete standard model generations in
the form of 16-plets of SO(10) and the Higgs fields as split multiplets. In
these notes, the emerging scheme of `local grand unification' and its
realization in the context of orbifold compactifications of the heterotic
string are reviewed.

23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat