Institute of Mathematics, University of Warsaw, ul. Banacha 2, 02-097 Warsaw, Poland
Abstract:
We prove that if ZFC is consistent so is ZFC + ``for any sequence of subsets of a Polish space there exists a separable metrizable topology on with , and Borel in for all .' This is a category analogue of a theorem of Carlson on the possibility of extending Lebesgue measure to any countable collection of sets. A uniform argument is presented, which gives a new proof of the latter as well.
Some consequences of these extension properties are also studied.