 Conditional wave function

In the spinless version of Bohmian mechanics, insert the actual environment configuration $Y(t)$ into a total wave function $\Psi (x,y,t)$ to obtain a subsystem's conditional wave function, when that slice is nonzero. It encodes the actual environment relevant to the subsystem's guiding dynamics. It need not satisfy an autonomous subsystem Schrödinger equation; further separation conditions are needed for an effective wave function.^[ref]