文档介绍：arXiv:hep-th/9706042 v1 05 Jun 1997
Abstract
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I. INTRODUCTION
There are a number of instructive models that can be exactly solved in the
limit where the number N of fields es very Well-known examples
include the linear and non-linear σ-models,2 the Gross–Neveu model3 and the
CP N−1 In four dimensions none of these models except the linear
σ-model are conventionally renormalizable, so their large-N limit has usually
been studied either by introducing an ultraviolet cutoff, or by working in two