- #1
Phiphy
- 16
- 1
The Feynman propagator in QFT is not zero for space-like separation, but we say this does not mean that causality is violated, we should check the commutator of field operators instead, and the commutators vanish for space-like separation.
My question is: why do we use commutators to check causality instead of propagators? Is there any examples that commutators are related to observation? And what is the 'causality criteria' for causality in classical relativistic field theory?
My question is: why do we use commutators to check causality instead of propagators? Is there any examples that commutators are related to observation? And what is the 'causality criteria' for causality in classical relativistic field theory?