from its environment, which comes out clearly in the formalism: in Eq. (34), it is the initial interaction of the system with the initial state that determines the coefficients ψ α S and the decoherence of the cosmological state into a superposition of eigenstates of system outcomes. The further interaction of the environment with the system simply acts to correlate the environment with those already established eigenstates (per the discussion on Eq. (32) and following). The basic assumption is that information flows from the system to its environment, not vice versa. This assumption is captured in Eq. (25) which states that the outcomes of interest for each subsystem depend only on particles outgoing “to the left” from each subsystem interaction operator in Eq. (23). As a result, we have been able to conveniently order subsystem interaction right to left (e.g, G$_{E}$G$_{S}$ in Sec. VI, G$_{E}$G$_{A}$G$_{S}$ in Sec. V and G$_{E}$G$_{B}$G$_{C}$G$_{D}$G$_{R}$ in Sec. VII) such that a subsystem is affected by the outcomes of subsystems to its right, but not by those to its left. That is, information effectively flows from right to left. This conception is directly related to Zurek’s observation regarding einselection on “the direction of information flow in decoherence, from the decohering apparatus and to the environment. . . ” [30]. This is opposite to the information flow of noise . In an idealized measurement situation, the desired information flow is that necessary for decoherence and the noise effect of the environment on the apparatus is ignored. With the convention of Eq. (25), the desired (“right to left”) information flow is carried by particles passing from one subsystem to the other on normal particle paths. In contrast, the undesired noise flows “backwards” (“left to right”), carried by particles along reverse particle paths. In both cases, however, the flow of information is along spacetime paths in the direction of increase in the path evolution parameter, regardless of whether this is forward or backward in time. This interesting connection between particle propagation along spacetime paths and the flow of information is a promising topic for future exploration. This appendix summarizes the full spacetime path formalism that is developed in detail in [25]. This full formalism provides a more rigorous underpinning for the more familiar Appendix A: Spacetime Path Formalism 30