IMPURITIES IN ONE DIMENSION

摘要

The renormalization and scaling arguments for the behavior of an impurity in a conformal invariant 1+1 dimensional field theory are reviewed by using simple examples in the field theory description of spin-1/2 spin chains. Particular attention is paid to the local structure of physical observable quantities like the magnetization around the impurity, which gives detailed informations on both the impurity and the excitations in the system. We then consider a more complicated impurity configuration which explicitly has two energy scale associated with them, namely two impurities that are separated by a certain distance with a fixed impurity coupling.