Effects of Quenching in \Delta I=1/2 Kaon Decays
  We present the inconsistencies which arise in quenched QCD in $\Delta I=1/2$ non-leptonic kaon decays using chiral perturbation theory (ChPT) to one loop. In particular we discuss how the lack of unitarity of the quenched theory invalidates the usual methods for the extraction of matrix elements from correlation functions. 
C.J.D. Lin, G. Martinelli, E. Pallante, C.T. Sachrajda and G.   Villadoro