Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Untwisted Moduli and Internal Fermions in Free Fermionic Strings   We investigate the dependence of the number and type of untwisted moduli on
the boundary condition vectors of relistic free fermionic strings. The number
of moduli is given by six minus the number of complex internal world--sheet
fermions and the type of moduli is determined by the details of the
world--sheet left--right asymmetry of the boundary conditions for the internal
fermions. We give a geometrical description of our results in terms of the
transformations of the compactified dimensions of $Z_2 \times Z_2$ orbifolds.
We investigate all possible boundary conditions for the internal fermions and
prove our results in general by showing that world--sheet supersymmetry
eliminates those boundary conditions which violate our results.

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The categories of this paper are: q-bio
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The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-ex
4
The categories of this paper are: cond-mat
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
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The categories of this paper are: eess
23
The categories of this paper are: solv-int