# Rajesh Gopakumar : exp(N)

The connection between large N gauge theories and string theories is
typically made perturbatively. Namely, the Taylor expansion in 1/N
corresponds to the genus expansion in string theory. Instanton effects in
the gauge theory, however, go like exp(-N) and correspond to
non-perturbative effects in the string theory. I will argue, in the
context of the N=4 super Yang-Mills theory, how very non-trivial large
N non-renormalization theorems in this instanton sector follow
simply from the dual string description. The argument assumes little other
than the existence of a derivative expansion in string theory. As a
particular example, one can explain the striking agreement found by
Dorey *et al* between certain weak coupling instanton calculations
and the strong coupling predictions of supergravity.

**Category**: String Theory**Duration**: 01:15:35**Date**: February 3, 2000 at 4:00 PM**Views**: 25-
**Tags:**seminar, String Theory Seminar

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