Massless fermions in multi-flavor QED_2
  The ground state of the multi-flavor 2-dimensional quantum electrodynamics (QED_2) is determined in the presence of finite baryon density, and it is shown that the model possesses two phases, the low density phase where the external baryon density is totally screened, and the high density phase, where the screening is only partial. The renormalization of the bosonized version of the model is also performed for both the zero and the finite density model giving massless multi-flavor QED_2 in both cases. 
S. Nagy