Interaction picture as any other operator. In particular, let and be the density matrices in the interaction picture and the Schrödinger picture respectively. If there is probability to be in the physical state |"ψ"〉, then Transforming the Schrödinger equation into the interaction picture gives 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. If the operator "A" is time-independent (i.e., does not have "explicit time dependence"; see above), then the corresponding time evolution for "A"("t") is given by In the interaction picture the operators evolve in
Non-physical entity many minds each person can have, which is not an issue for physicalism which can simply declare one-mind-per-person almost by definition; and whether non-physical entities such as minds and souls are simple or compound, and if the latter, what "stuff" the compounds are made from. Describing in philosophical terms what a non-physical entity actually is (or would be) can prove problematic. A convenient example of what constitutes a non-physical entity is a ghost. Gilbert Ryle once labelled Cartesian Dualism as positing the "ghost in the machine". However, it is hard to define in philosophical terms what it is, precisely, about