A relativistic framework in which the measurement event is modelled as a geometric incidence between a null quantum system (a photon, represented over projective null twistor space ℙN) and a timelike observer worldline in Minkowski space. The observer's forward temporal orientation is supplied not thermodynamically but as a discrete geometric datum fixed by the temporal orientability of Minkowski space. Global evolution remains unitary; the only irreversibility is a causal monotone of second-law type with no finite non-relativistic limit. The central claim — that the temporal arrow of collapse can be supplied purely geometrically while preserving unitarity — is stated as a falsifiable question with two valid answers, and the deciding experimentum crucis is specified but not yet executed. The claim is therefore left explicitly open.
Pablo Domínguez Delmás (Sun,) studied this question.