Topos-theoretic Model of the Deutsch multiverse
  The Deutsch multiverse is collection of parallel universes. In this article a formal theory and a topos-theoretic model of the Deutsch multiverse are given. For this the Lawvere-Kock Synthetic Differential Geometry and topos models for smooth infinitesimal analysis are used. Physical properties of multi-variant and many-dimensional parallel universes are discussed. Quantum fluctuations of universe geometry are considered. Photon ghosts in parallel universes are found. 
Alexander K. Guts