FLUIDIFICATION OF QUIVERS AND THE TIETZE EXTENSION THEOREM FOR DIAGRAMS OF TOPOLOGICAL SPACES

For quivers with no directed cycles, the concept of fluidification is defined and used to prove that, under corresponding assumptions, the Tietze extension theorem for diagrams of topological spaces modeled on such quivers holds. Another application of the given concept of fluidification -is a characterization of certain diagrams of proper maps.