Dreams as Displacement Reprocessing: REM Sleep, Narrative Ground State Navigation, and the Overnight Resolution of Unfinished D(xi)

REM sleep is the organism's offline displacement reprocessing system. Unresolved D(xi) from waking becomes dream emotional substrate; the narrative is a search through configuration space for return paths to S0 at zero behavioral cost. Nightmares are wrong attractors in dream space. PTSD nightmares are displacement too large for the offline simulator to resolve. The overnight displacement reduction effect (Walker 2009) is formalized as D(xi_emotional) reduction via norepinephrine suppression during REM replay.