An Introduction to Quantum Order, String-net Condensation, and Emergence   of Light and Fermions
  We review some recent work on new states of matter. Those states cannot be described symmetry breaking and hence contain a new kind of order -- quantum order. Some quantum orders are shown to be closely related to string-net condensations. Those quantum orders lead to an emergence of gauge bosons and fermions from pure bosonic models. 
Xiao-Gang Wen