Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fermion Hilbert Space and Fermion Doubling in the Noncommutative
  Geometry Approach to Gauge Theories   In this paper we study the structure of the Hilbert space for the recent
noncommutative geometry models of gauge theories. We point out the presence of
unphysical degrees of freedom similar to the ones appearing in lattice gauge
theories (fermion doubling). We investigate the possibility of projecting out
these states at the various levels in the construction, but we find that the
results of these attempts are either physically unacceptable or geometrically
unappealing.

14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
4
The categories of this paper are: cond-mat