On fermionic tilde conjugation rules and thermal bosonization. Hot and   cold thermofields
  A generalization of Ojima tilde conjugation rules is suggested, which reveals the coherent state properties of thermal vacuum state and is useful for the thermofield bosonization. The notion of hot and cold thermofields is introduced to distinguish different thermofield representations giving the correct normal form of thermofield solution for finite temperature Thirring model with correct renormalization and anticommutation properties. 
S.E. Korenblit, V.V. Semenov
hep-th