Ultrafiltres absolus
Uniform Transformation Groups on Lower Dimensional Spaces.
Urysohn universal spaces as metric groups of exponent 2
The aim of the paper is to prove that the bounded and unbounded Urysohn universal spaces have unique (up to isometric isomorphism) structures of metric groups of exponent 2. An algebraic-geometric characterization of Boolean Urysohn spaces (i.e. metric groups of exponent 2 which are metrically Urysohn spaces) is given.