A PHYSICAL EXPLANATION FOR THE TILDE SYSTEM IN THERMO FIELD DYNAMICS

DONG MI, HE-SHAN SONG, YING AN
2001 Modern Physics Letters A  
For a two-body quantum system, any pure state can be represented by a biorthogonal expression by means of Schmidt decomposition. Using this in the composite system which include a thermodynamic system and its surroundings, it is found that the tilde system in thermo field dynamics is just the surroundings of the real system.
doi:10.1142/s0217732301003607 fatcat:pirahpxy5bgtrbgc4lozmzeliq