Space-time symmetries and internal quantum symmetries can be placed on equal
footing in a hyperspin geometry. Four-dimensional classical space-time emerges
as a result of a decoherence that disentangles the quantum and the space-time
degrees of freedom. A map from the quantum space-time to classical space-time
that preserves the causality relations of space-time events is necessarily a
density matrix.Comment: 9 pages, to appear in the Proceedings of the 2nd International
Symposium on Information Geometry and its Application
