Surprises in nonperturbative dynamics in sigma-model at finite density
  The linear $SU(2)_L \times SU(2)_R$ sigma-model occupies a unique place in elementary particle physics and quantum field theory. It has been recently realized that when a chemical potential for hypercharge is added, it becomes a toy model for the description of the dynamics of the kaon condensate in high density QCD. We review recent results in nonperturbative dynamics obtained in the ungauged and gauged versions of this model. 
V. P. Gusynin, V. A. Miransky and I. A. Shovkovy