Classical/Quantum Duality

Abstract

String theory requires two kinds of loop expansion: classical $({\alpha }^{\prime })$ worldsheet loops with expansion parameter $<T>$ where $T$ is a modulus field, and quantum $(\hslash )$ 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.

Comments: 5 pages latex, NI-94-016, Typographical errors corrected