Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Classical/Quantum Duality   String theory requires two kinds of loop expansion: classical $(\alpha')$
worldsheet loops with expansion parameter $<T>$ where $T$ is a modulus field,
and quantum $(\hbar)$ spacetime loops with expansion parameter $<S>$ where $S$
is the dilaton field. Four-dimensional string/string duality (a corollary of
ten-dimensional string/fivebrane duality) interchanges the roles of $S$ and $T$
and hence interchanges classical and quantum.

18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int