Student Friendly Introduction to QFT · Problem 7.7

QED: Quantum Field Interaction Theory Applied to Electromagnetism

Physics — QFT · interaction-picture-hamiltonian

Problem

Show that

H_I^I = U_0^\dagger H_I^S U_0 = H_I^S

only if

H_I^S

commutes with

H_0

. The last part of Box 2-3 in Chap. 2 (pg. 27) may help.