Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Duality and Orbifolds   We construct several examples where duality transformation commutes with the
orbifolding procedure even when the orbifolding group does not act freely, and
there are massless states from the twisted sector at a generic point in the
moduli space. Often the matching of spectrum in the dual theories is a result
of non-trivial identities satisfied by the coefficients of one loop tadpoles in
the heterotic, type II and type I string theories.

21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph