Advanced Quantum Mechanics Schwabl · Problem 2.6

Bosons

Physics — Quantum Mechanics · fermi-operator-relations

Problem

Derive the following relations for Fermi operators: a) e−αa†a eαa†=a−α2a†+α(aa†−a†a)e^{-\alpha a^\dagger}a\,e^{\alpha a^\dagger} = a - \alpha^2 a^\dagger + \alpha(aa^\dagger - a^\dagger a) e−αaa†eαa=a†−α2a−α(aa†−a†a)e^{-\alpha a}a^\dagger e^{\alpha a} = a^\dagger - \alpha^2 a - \alpha(aa^\dagger - a^\dagger a) b) eαa†aa e−αa†a=e−αae^{\alpha a^\dagger a}a\,e^{-\alpha a^\dagger a} = e^{-\alpha}a eαa†aa†e−αa†a=e−αa†.e^{\alpha a^\dagger a}a^\dagger e^{-\alpha a^\dagger a} = e^{-\alpha}a^\dagger.

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