Editing Interaction picture (section)

====Time-evolution of states<!--'Schwinger–Tomonaga equation' redirects here-->====

Transforming the [[Schrödinger equation]] into the interaction picture gives

:<math> \mathrm{i} \hbar \frac{\mathrm{d}}{\mathrm{d}t} |\psi_\text{I}(t)\rang = H_{1,\text{I}}(t) |\psi_\text{I}(t)\rang, </math>

which states that in the interaction picture, a quantum state is evolved by the interaction part of the Hamiltonian as expressed in the interaction picture.<ref>Quantum Field Theory for the Gifted Amateur, Chapter 18 - for those who saw this being called the Schwinger-Tomonaga equation, this is not the Schwinger-Tomonaga equation. That is a generalization of the Schrödinger equation to arbitrary space-like foliations of spacetime.</ref> A proof is given in Fetter and Walecka.<ref>{{cite book |last1=Fetter |first1=Alexander L. |last2=Walecka |first2=John Dirk |title=Quantum Theory of Many-particle Systems |date=1971 |publisher=McGraw-Hill |isbn=978-0-07-020653-3 |page=55 |url=https://books.google.com/books?id=Y1HwAAAAMAAJ |language=en}}</ref>