I am using Mandl and Shaw and Lahiri to get an introduction to QFT. Something I haven't seen discussed much or at all is whether the commutators or anti-commutators vanish for the normal ordering of a product of different field operators. As a concrete example, let's say that I want to normal order [itex] \bar \psi^- \psi^+ \phi^-[/itex], where [itex]\psi[/itex] is fermionic and [itex]\phi[/itex] is bosonic. Does the term pick up a minus sign or not and why?(adsbygoogle = window.adsbygoogle || []).push({});

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# Normal ordering in an interacting field theory

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